I'am installing the witcher 3 and my download stops at 92.4%
why is that happening

Are you installing it from a DVD, through Galaxy or did you download the files manually?

I just bought a new graphics card from newegg and i got the witcher with the graphics card. Then i redeemed my code on the geforce page. Then i whent on gog.com and downloaded the galaxy and from there i installed the game

Try closing the client and re-opening it again first. Do you see the game being installed at all or it disappeared completely?

it is done installimg but why can't i play. It is at 100% but i can't press the play button

I have same problem I bought the game tried to install it but it after a while box poped up saying -3 checksum error so i tried to download it from gog but then when i had 100 percent downloaded i could not click on play button