How To Help The Child To Adopt Proper Behaviour?

My son is 7 yrs old. He is doing great academically. He has a friend at school who is 5, & he is taking on his behavior. Baby talk, talking gibberish & hugging everyone. He has a very hard time focusing, & is very fidgety. How do I explain proper behavior towards others, & help him with focusing if I cant correct behavior of his friend?