Thanks for the help.
Already playing with "sp_hellgate000". Made a mistake and only saved the whole hellgate folder in steam but not the savegames.
I replaced the "sp_hellgate000.dat" and "sp_hellgate000.idx" for the sp_hellgate_1337 files. Then I got an error and the game did not start. Tried both files together. The game started, but the bag space was limited. Last step was that i removed the new part and copied both files from the old version which I saved before . Now I can scroll the bags again, but every item under the additional bags in the inventory is lost.
Do I need to make a complete new game to install this mod?