various BSOD after ~5min in any game

If you can set the voltage, sure do it :)

Please run the tool again and upload the zip file.

Please set the voltage back to 1.2V, higher is not supported and causes problems.

The 0xEF could have been caused by a few things, like malware, a damaged hard drive, CPU problems and some other things.

Please download and install Malwarebytes free (Uncheck trial version in the installation process)
Please run a threat scan with Malwarebytes, a full scan with your AV, scan your system with Adwcleaner and Kaspersky TTDSKiller.

Diagnostics Test

 HDD & SSD TEST

Run SeaTools to check the integrity of your HDD. SeaTools for DOS and Windows - How to Use - Windows 7 Help Forums

   Note

Do not run SeaTools on an SSD as the results will be invalid.

Run chkdsk Disk Check - Windows 7 Help Forums

Diagnostic Test

 CPU TEST

Run Prime95 to stress test your CPU. Prime95 - Stress Test Your CPU - Windows 10 Forums

   Note

If you're overclocking anything, please stop it and set everything back to default while troubleshooting

   Warning

Your CPU temperatures will rise quickly while under this stress test. Keep a keen eye on them and abort the test if overheating occurs.

AndiElse96 said:

couldn´t it be easier to format my harddrive and erease all data? i dont have that much installed yet anyways... But i´ll do what you wrote for now!

set everything in the BIOS back to normal already

You could RMA the part that is causing it, but we first need to find it.

Erasing and formatting the hard drive probably won't help, because it looks a lot like a hardware problem.