Need information on No Trespassing signs and preventing neighbors from entering my gate (Oregon, USA)

I’ve never had to put up a No Trespassing sign and I’ve always thought they would be perceived as “unfriendly.” However, I’m feeling harassed in my new living situation.

I currently have a situation with an autistic adult neighbor and their mom. The son has shown unwanted interest in me and has entered my gate to knock and/or ring for non-emergencies. The last time I know for certain that he did this was at 9:30pm after dark. He emerged when I went out to my car around 11pm and that’s when he revealed he had knocked to ask me how I slept the night before. I asked him to never enter my gate/knock again, citing my anxious cat. The next day his mom entered my gate, rang my bell, then left my gate wide open. The day afterwards, someone entered the gate again and left a small gift at my doorstep. I am guessing it was the son but it very well could have been a child. Someone also wrote(in dust) a giant “X” on my vehicle’s front and back windows. Again, could be kids, though I’ve only seen kids passing by once. I share a carport with the neighbors and they walk past my vehicle to get to their own gate.

It’s been over a week and I haven’t witnessed them entering my gate so I think they’ve gotten the point.

Note: the gate can’t be locked and is used for deliveries. I’m chronically ill so it’s important that my packages are delivered to my door. I believe it’s also in my lease that I can’t add a lock.

Legal questions:

To legally keep them from entering my gate, does it have to be a No Trespassing sign or does a No Soliciting sign work as well?

If they violate it, do I have to get it on camera to enforce it?

Lastly, if I file a police report after any violations or continued unwanted interest(commenting on my appearance, talking my ear off, observing me/watching me) from the son, how does a restraining order against a neighbor you share a building and carport with work? They often hangout in the carport or beside it and the son parks behind his mom’s car which puts him in front of my fenced area and looking into my bedroom.

Location: Oregon