There is a "recovery" option that will set your files back to a previous installation to fix problems. You pick the date which varies according to the last time you changed your security settings. Just type "recovery" or "restore" in the search option.
Hi newcomer and welcome to the Tom's hardware forum.
1- CRTRL +shift + esc = Task manager, file, new task and write explorer, hit enter.
2- After the 1st step, check in process if exist someone that is using all the RAM or Processor.
3- Start in safe mode, and use your antivirus, ccleaner and malwarebytes.