/3/ - 3DCG

Can anyone help me please? Downloaded blender to add some effects on video, but stuck with rendering that completely ruins output video. In VSE cutting and rendering videos does good. But when I try to render video from composition mode or straight from 3d view - it renders completely rekt just like on webm.
I've tried almost everything that tutorials suggest, nodes, video on plane, video as background, changing blender render to cycles, changing format and fps etc, etc.
Even when i try to play video from timeline in 3d view - it lags and first frames apper in a middle of vid, sometimes looped, sometimes freezing, also watch webm. I've already spent like 7 hours trying to figure shit out. Even switched to another laptop with another OS and installed previous version of blender - no luck, having same issue on it as well.