With the help of Cyro-Utilitis (recommended settings) the game now runs stable. For my Steam friends I just play "Rockstar Launcher" all the time... and the Steam overlay is also only for the launcher and not the game. Additional the SteamDeck shows me that I have 3 (!!) windows ...
1. Open a command window “Run” by pressing «Win + R» and then enter the command:steam://open/console. 2. Type this into your Steam Console:download_depot 1174180 1174184 5805888981794472260 3. The rollback files will get downloaded once you get the following message. Depot download ...