Sorry, wrong language, but I don't speak German and I am reading an automatic translation of your posts :(.
Could you give some more details on the bug check you are encountering? Is it a 0x1A: MEMORY_MANAGEMENT, or 0x50: PAGE_FAULT_IN_NONPAGED_AREA, or both? Are there any more details, for example the component that forced the bug check? Check the Event Viewer (in particular the System log and the Administrative Events filter) for details.
The Blue Screen troubleshooter might help, but I would suggest trying out the steps suggested in the second bug check.
Also, despite running the memory checker, I would still suggest trying it out with different memory (for example, if you have enough memory, remove half of it, then the other half...). If you are running a third party anti-virus (in particular if it is not a recent version or not from one of the primary vendors), try running with it deactivated. Make sure you have the latest version of your BIOS (UEFI, I presume)
This is unlikely to be easy to resolve, and will probably require a fair amount of trial and error. Still at this point, I would think we are dealing with a hardware issue :joystick: