I don't feel like helping my classmate
Why don't you want to help your classmate?
My classmate lies about various things
Your classmate needs help and if you can help, then you should give your assistance. You are being selfish by not helping when you have the power to do so.
I'm going to hang out with this classmate some more and eventually he will hate me.
Your classmate will appreciate the time you invested in helping by hanging out with that person.