you have obviously got hit by something , don't be offended but you don't have to go on porn sites to get this to happen to you , I got ransomware on a spare pc on a games site.
you need to save all the things you don't want to loose and look in your list of programs for the recovery console , reboot your pc to a never used state.
the code for some ransomware is so complicated that some anti virus people admit they cant crack it.
DO NOT pay any money all they want is your bank details to clean you out , they wont take the $500 they will take everything.
Also do you really think they will delete everything they put on your pc , if they don't they will pay you another visit.
REBOOT TO FACTORY SETTINGS IS THE ONLY SAFE OPTION.