My son is 2y.o and 3 month. He don't let me to brish his teeth and he himself does not do it as well. I am afraid of caries. What to do?

Seek professional he. At 2y3mo old your son is more than a year past due for his 1st Dental Examination. This is a behavior management issue as well as a threat to your son's dental health. Please contact a Specialist (rather than a General Dentist), a Pediatric Dentist, and make an appointment. A Pedodontist is superbly trained to help manage problems like your son's. Don't wait, call now.
Whose in charge? I suspect you wouldn't let him take a crap in your front room while guests are over. In the same you don't need to let him control you with this. Let him pick out a type of brush and or paste, but his control stops there. Sit with him doing it until you are happy with the job. If he stops too soon or doesn't do it right make him start over. It is worth the effort and not abusive.
Short Elmo Game. About tooth brushing. Just make it fun get a fun toothbrush with Elmo picture and his own toothpaste and make it fun. If concerned see a pedodontist.
Train him. You are in charge. You have to teach him or suffer the results. Make it a game.