You MUST have the LATEST drivers for the graphics card, this can easily be done be visiting the manufacture's website. Second, what program you're using for the GPU benchmark testing?
Relevant Skills and Experience
If the drivers for the GPU are outdated, stress testing the GPU can cause instability issues with windows 10, which in turn causes the computer to crash (BSOD) due to thermal shut down.
Proposed Milestones
€15 EUR - update the GPU drivers to the latest version (IF AVALIABLE).
€19 EUR - Retest GPU. If it still crashes, computer may be full of dust. Hire local technician to clean.