In which folder does the video have to go?

I want to drag a video from my laptop to my smartphone. But no matter what folder I put it in, it doesn't appear on my phone. It is a normal MP4 file.

Just open the video on your smartphone with a file explorer.

E.g. With https://play.google.com/...e.explorer

Sorry but I only understand train station

Look at the edit.

I've done that now and the video is on it too but I can't see it, just hear it.

Which app does it work on?

I can only select photos. So in the gallery

But it has a picture on the PC?

Yes