How to read the next document on firebase when button is pressed

I am trying to build an app where the user has the option to pass card and read some activities passing flashcards. I can only show the first card but I don't know how to remove the first one and show the next document. How can I remove the first document item that is showing and move to another document when I pass the first card? I am able to show the first one but I can show the others documents from firrstore.

    return StreamBuilder(
      stream: firestoreInstance
          .collection('categorias')
          .doc(widget.category.toString())
          .collection('Subclass')
          .doc(widget.docId)
          .collection('Cards')
          .snapshots(),
      builder: (context, snapshot) {

        if (snapshot.data == null)
          return Center(child: CircularProgressIndicator());

        if (snapshot.data.docs.length == 0) {
          return Center(
            child: const Text(
              '',
              textAlign: TextAlign.center,
            ),
          );
        } else {
          snapQuery = snapshot.data.documents[0];

          String description = snapQuery.data()['description'];
          String title = snapQuery.data()['title'];
          String font = snapQuery.data()['fonte'];
          String obs = snapQuery.data()['obs'];
          String tema = snapQuery.data()['tema'];
          String cat = snapQuery.data()['cat'];

          return Card(
              elevation: 0,
              margin: EdgeInsets.only(left: 32.0, right: 32.0, top: 20),
              color: Color(0x00000000),
              child: FlipCard(
                  flipOnTouch: false,
                  key: cardKey,
                  direction: FlipDirection.HORIZONTAL,
                  speed: 1000,
                  onFlipDone: (status) {
                    print(status);
                  },
                  front: Container(
                    decoration: BoxDecoration(
                      color: Colors.white,
                      borderRadius: BorderRadius.all(Radius.circular(8.0)),
                    ),
                    child: ListView(
                      children: <Widget>[
                        Row(
                          crossAxisAlignment: CrossAxisAlignment.start,
                          children: [
                            Padding(
                              padding: const EdgeInsets.only(top: 16.0),
                              child: Image.asset(
                                'images/law_icon.png',
                                width: 69,
                                height: 69,
                              ),
                            ),
                            Flexible(
                              child: Padding(
                                padding: const EdgeInsets.only(top: 32.0),
                                child: Text(
                                    title,
                                    textAlign: TextAlign.start,
                                    style: TextStyle(
                                        fontSize: 21,
                                        fontFamily: 'Notosans',
                                        fontWeight: FontWeight.normal)),
                              ),
                            ),
                          ],
                        ),
                        SizedBox(
                          height: 200,
                        ),
                        Expanded(
                          child: Align(
                            alignment: FractionalOffset.bottomCenter,
                            child: Container(
                              padding: EdgeInsets.symmetric(horizontal: 10),
                              width: MediaQuery.of(context).size.width,
                              height: 100,
                              child: adFront == null
                                  ? Image.asset(
                                      'images/anuncie.png',
                                      fit: BoxFit.cover,
                                    )
                                  : Image.network(
                                      adFront,
                                      fit: BoxFit.cover,
                                    ),
                            ),
                          ),
                        ),
                        SizedBox(
                          height: 10,
                        ),
                      ],
                    ),
                  ),
                  back: Container(
                    decoration: BoxDecoration(
                      color: Colors.white,
                      borderRadius: BorderRadius.all(Radius.circular(8.0)),
                    ),
                    child: Stack(
                      children: [
                        ListView(
                          children: <Widget>[
                            Container(
                              width: MediaQuery.of(context).size.width,
                              height: 40,
                              color: Color(0xff007487),
                              child: Center(
                                child: Text(
                                  tema,
                                  textAlign: TextAlign.start,
                                  style: TextStyle(
                                      fontSize: 18,
                                      fontFamily: 'Notosans',
                                      fontWeight: FontWeight.normal,
                                      color: Colors.white),
                                ),
                              ),
                            ),
                            Flexible(
                              child: Padding(
                                padding: const EdgeInsets.symmetric(
                                    horizontal: 12.0),
                                child: Text(
                                    cat,
                                    textAlign: TextAlign.start,
                                    style: TextStyle(
                                        fontSize: 18,
                                        fontFamily: 'Notosans',
                                        fontWeight: FontWeight.normal)),
                              ),
                            ),
                            Padding(
                              padding: const EdgeInsets.all(12.0),
                              child: Text(
                                description,
                                textAlign: TextAlign.start,
                                style: TextStyle(
                                    fontSize: 12,
                                    fontFamily: 'Notosans',
                                    fontWeight: FontWeight.bold),
                              ),
                            ),
                            SizedBox(
                              height: 20,
                            ),
                            Padding(
                              padding: const EdgeInsets.all(12.0),
                              child: Text(
                                obs,
                                textAlign: TextAlign.start,
                                style: TextStyle(
                                    fontSize: 12,
                                    fontFamily: 'Notosans',
                                    fontWeight: FontWeight.normal),
                              ),
                            ),
                            SizedBox(
                              height: 10,
                            ),
                            Positioned(
                              child: Align(
                                alignment: FractionalOffset.bottomCenter,
                                child: Container(
                                  padding: EdgeInsets.symmetric(horizontal: 12),
                                  width: MediaQuery.of(context).size.width,
                                  height: 100,
                                  child: adBack == null
                                      ? Image.asset(
                                          'images/anuncie.png',
                                          fit: BoxFit.cover,
                                        )
                                      : Image.network(
                                          adBack,
                                          fit: BoxFit.cover,
                                        ),
                                ),
                              ),
                            ),
                            SizedBox(
                              height: 2,
                            ),
                            Align(
                                alignment: FractionalOffset.bottomCenter,
                                child: Padding(
                                  padding: const EdgeInsets.all(10.0),
                                  child: Text(
                                    font,
                                    style: TextStyle(
                                        fontSize: 12,
                                        fontFamily: 'Notosans',
                                        fontStyle: FontStyle.normal),
                                  ),
                                )),
                          ],
                        ),
                      ],
                    ),
                  )));
        }
      },
    );