1. install GTR2 in STEAM
2. copy GTR2 directory from "c:\progamme (x86)\steamapps\common\GTR 2 - FIA GT Racing Game" into any directory (for me c:\games\gtr2"
3. install the European patch over the new directory (https://www.racedepartment.com/downloads/ european-v1-1-patch-for-gtr-2.14173/)
3. install NO-CD patch over the new directory (https://www.racedepartment.com/threads/no-cd- patch-for-gtr-2.132546/)
4. run Autoupdater over the new directory (if necessary delete the profile from the archiv\userdata before to move the updater to the new installation, it uses downloads already made)
5. install xd tool if necessary (https://www.racedepartment.com/downloads/gtr2-xd- 2-16-map-plugin.23763/)
7. right mouse button on GTR2 / show product key / copy product key in Steam-Client
6. start game and set realism to "Simulation
7. start Multiplayer and insert the copy key from Steam at the serial number with Ctrl+C
8. if no KBB lobby account exists yet, create a new one.
9. finished
additionally you still need to install the 1.1 patch. which is not included in the Steam version. see point 3
Glück auf!