Hello smeraldan and welcome to Seven Forums.
My usual disclaimer: I'm not an expert at anything. Sometimes malware can prevent Windows Updates from installing. Run a full scan with your personal anti-malware suite. Then use the free Malwarebytes to run another full scan. (No anti-malware product is 100% effective 100% of the time. If there was such a thing we'd all be using it.)
Malwarebytes
Another possible problem is if system files became damaged or corrupt. I'd run a system file checker scan from an elevated command prompt (option two.) If problems are found run the scan 3 times rebooting in between each scan.
SFC /SCANNOW Command - System File Checker
You could also try running the System Update Readiness Tool if you haven't already done so.
System Update Readiness Tool fixes Windows Update errors in Windows 7, Windows Vista, Windows Server 2008 R2, and Windows Server 2008
Try installing the updates again, but this time just do a few at a time (maybe only 5 or so.) Keep track of the KB numbers. Start with the critical updates, then the important, and save the optional for last. If a group of 5 installs OK go on to the next group. If any group fails to install you'll know which group to uninstall. Try installing just one update at a time. If they install OK go on to the next group. Otherwise just ignore the problem update(s) for the time being and continue installing in groups of 5.