Hello everyone and sorry for my bad englisch.

If you use more then 2 accounts for GTA like me but got them on different plattforms,
for example you bought your 2nd gamekey fia a random keyselling site and its a non steam key,
you will have to activate the key on an rockstar account.

And here comes the big problem.
You cant log in with the new created account on the steam version you've already installed.
If you log in into the super awesome new Rockstar launcher you have to download the non steam version of the game or switch back to the other account to launch the game.
I tried to contact the support about this and asked them friendly if it is somehow possibleand as you all know this support is just the best on this mf plannet so they helped me out by replying with the following text:

Hello,Dear ...

Thank you for contacting Rockstar Support.

We understand that you are facing performance issues with our title. We kindly request you to follow the below troubleshooting steps which can resolve the issue.

We always recommend keeping your video card drivers up to date with the latest version.
The latest drivers for NVIDIA cards are located here and the latest drivers for AMD cards are available here.
Once you arrive on the page for your video card manufacturer, you can fill out the form and download the appropriate driver for your card.

Best regards,

CrOCKstar Support

After updating my mf drivers i threw my pc at my face and it worked.
I somehow logged in with my new Rockstar account (still only the steam version installed), opened the installation folder, and started the file "PlayGTAV.exe".
After some hours on the floor i realized some modder caged me and took me to there underground Base somewhere in Los Santos.

After escapeing them i wrote a thankfull email to Rockstar for helping me with the drivers issue.