How do you stop being weird and creepy ?

(16M) I am autistic, I have no idea of how to interact with others.

Everytime I talk, I say nonsense, I tried to engage in random conversations even with people I don’t know. For example, if someone sitting next to me is talking about cars, I would just give them a fun fact about cars. Even if I never talked with that person, and usually, when I apologise for intruding conversations like that, people say that they don’t mind (which I doubt).

One time as I was sitting alone at lunch, a group of guys told me to not sit alone and to come with them. I said nothing the whole conversation. They slowly started to look at each other in an awkward way, like they expected me to talk or something, then I heard one of them saying something about me and others started to giggle. At that point, I didn’t know what to say and I was too scared to screw up my only opportunity to make friends.

I started following those guys around at recess, just silently without saying a word. I consider them as my friends, but they started to ignore me lately. Recently, one of them just told me to stop following them like that because it makes them uncomfortable, so I stopped.

By saying nonsense, I mean that when I talk, I stutter a lot, talk for too much, and always make random conversations about deep subjects by including philosophy etc..

Any advice? I feel way too behind in social interactions, yet, when I am talking with my younger brother, I always come off as normal.