I recently installed ScummVm and added the free games, which just worked fine.
But I also wanted to add some of my GOG Games and it seems I'm just noch clever enough:
Could so. help me and tell me, what to do exactly?
The games I downloaded from gog are just .exe-files which aren't being recognized by Scumm.
When I install the game on my PC and copy the whole order to my mobile, I'm able to choose the folder, but Scumm tells me that there isn't a game in this folder.

So what do I have to do?

Thanks in advance!

The only files needed are described in the ScummVM wiki: https://wiki.scummvm.org/index.php?title=Datafiles#Indiana_Jones_and_the_Fate_of_Atlantis

You can find there the files needed for any other supported game. An asterisk ( * ) means "all", in a manner, so *.LFL for example, means all files than have the LFL extension.

Once a GOG version is installed in a PC it is quite simple to find the files; they will all be inside the same folder, which is not the root folder of the installation, but another within it. That is why ScummVM did not recognize the game inside the folders you copied, although the needed files are somewhere in there.