meanwhile I installed a RTX 2070 with 8gb vram. The problem is still there. When I close premiere, it remains in the task manager with 8-9% of cpu usage.
EDIT: The problem was nahimic/realtek sound driver. I came to the solution because houdini was also crashing with the report of a segmentation failure.
Updating to the newest sound driver (it restarts the computer twice) solved the problem. Now Premiere works properly and doesnt stay in the task manager with 8-9% cpu usage.