So i tried this command from windows

(echo file 'first file.mp4' & echo file 'second file.mp4' )>list.txt
ffmpeg -safe 0 -f concat -i list.txt -c copy output.mp4

while making a batch file

Then i concatenate two video’s and as soon as the one video ended. It changes resolution, then the video player started to glitch out pixel’s like in vlc.