RE: friends who dont like my hobby
Ok, well, I guess I'm one of the old guys so I don't know how much any advice I have for a 15 y/o will really help but I'll give you some thoughts anyway.
I started with models at 10 y/o when my dad me a nitro powered line control plane. I've been in the hobby off and on since - some 46 years...
Kids can be mean, if they see something that they say/do bothers you they will keep harping on it.. So, if you can, just let it roll off your back. Or better yet, make fun of yourself for it too. Arguing or trying to get back at them will only confirm they are getting to you and they will keep it up.
As others said, try a local hobby shop or track to find like minded people. Keep in mind here that friends do not have to be your age. They can be older or younger. For example, one of my very best friends in the world is only 3 years older than my son and we (wife and I) regularly hang out with a couple that is older than our parents.
Maybe go to a teacher at school, like a shop teacher - do you still have shop class? Anyway, ask about starting an RC club. You might be surprised to find some more kids at your school who would find the hobby interesting.
As was also said above, take them to a track to watch a race, or a flying field to watch the planes. It may expand their views and yours too.
At 15 you're probably starting to think about real cars. Take the knowledge that RC cars have given you and start to apply it to the real world. Sure RC stuff is simplified but the underlying science of chassis design and set up, steering, gearing, etc is very similar. Use what you already know as a basis and soon those same people that make fun of you may be coming to you for repair and set up advice on their real cars.
Anyway, this CAN be a lifelong hobby and 99% of the people I knew in school I have had zero contact with since I graduated High School.
So, Good Luck and if you like something try not to let any haters talk or intimidate you out of it.