Is it possible to add games already downloaded on to galaxy? I had a few games on galaxy and had to delete the client after having problems with the witcher 3. After installing galaxy again however there is no option to scan for games.

It is possible. Go into galaxy library, click the game you have installed, click more, go to manage, then import folder. You can then select the folder where you have it installed and galaxy will se it as installed.

Did the trick, thanks