Same here but I think it is just as well we can have this conversation in public. First of all, take screen shots of whatever you already have and back it up on a hard drive. If it’s text messages and it shows his contact name, make sure his cell phone number is visible in the screen shot (might mean removing his name from your contacts.) This strengthens your evidence.
Change your cell phone number. This is the worst part but one need not be bright or tech savvy to harass someone else using their mobile number these days. They just need to know your digits. My stalker was into coding. I got a separate cell phone that I used exclusively for 2-factor authentication on my accounts — including banking. Nobody knew the number.
You should make yourself as boring as possible online. If you haven’t, kick this guy off your social media and turn your settings private. Don’t use your face as your profile photo. Don’t share anything about your daily routine because he might be lying to your acquaintances.
Lastly, don’t expect people — friends, coworkers or law enforcement — to take be sympathetic. For some reason, people’s first instinct is to downplay what is happening. It’s not your job to convince any of them. Even law enforcement, you just need to file a complaint. Where I live, restraining orders are only issued by a judge. You should find out what your country’s laws are.
I forgot - self defense classes