How to WriteFile in AvsPMod

I'm very new in working with video editing via AviSynth script editor AvsPmod v2.6.3.4 and I want to add some MP4 videos to a big one but WriteFile creates a file with no content. VLC player results in error 0xc00d36c4 file cannot be played back. Starting the 27MB video with DirectShowSource WriteFile creates only 31KB mp4 output but with the same error. My understanding of WriteFile does not seem right. What is the best command to combine about 30 mp4 files?

The code:

LoadPlugin("c:\Program Files\AvsPmod\plugins\x86\ffms2.dll" )

file01="c:\Users\MD\Videos\2020-08-01 19-38-53_01.mp4"
fileErg01 = "c:\Users\MD\Videos\2020-08-01 19-38-53_01_erg.mp4"
file02="c:\Users\MD\Videos\2020-08-01 19-47-34_02.mp4"
fileErg02 = "c:\Users\MD\Videos\2020-08-01 19-47-34_02_erg.mp4"
file03="c:\Users\MD\Videos\2020-08-02 16-23-00_03b.mp4"
fileErg03 = "c:\Users\MD\Videos\2020-08-02 16-23-00_03b_erg.mp4"

FFmpegSource2(file01, vtrack = -1, atrack = -1, timecodes="timecodes_file.txt").Trim(0,2300).FadeOut(15).WriteFile(fileErg01, "current_frame", "test", false, true)
FFmpegSource2(file02, vtrack = -1, atrack = -1, timecodes="timecodes_file.txt").Trim(0,2000).FadeOut(15).WriteFile(fileErg02, "current_frame", "test", false, true)
FFmpegSource2(file03, vtrack = -1, atrack = -1, timecodes="timecodes_file.txt").Trim(0,2600).FadeOut(15).WriteFile(fileErg03, "current_frame", "test", false, true)
DirectShowSource(file01).Trim(0,2300).fadeout(15).WriteFile(fileErg01, "current_frame","test", false, true)

Thanks for the help