Use a system restore point if you have one.
This won't help you directly at this stage from what you've said, so for reference only:
Accessing Safe Mode in Win 10 is not by hitting F8 on boot by default. (My boot time to the lock screen is around 13s - no time). You access Safe Mode typically by SHIFT + Restart and navigating thru a sequence of prompts, or by booting from Win 10 install medium, and via Repair thrua similar sequence of prompts.