Edvice on how to make a relationship better from an experienced adult!? Please?

We have been dating a year and six months. Things have been going down fall. For some reason we don't trust each other well we haven't cheated but like we still have issues. The problems I see in her is she is more stubborn she has less contact with me as everyday goes and when she gets mad she is rude ignorant and just plain angry. My problems I get mad when she says stupid commets she gets mad I am always trying to talk things out and she gets lissed that I complain why she is on twitter having other conversations when I am trying to talk to her on the phone. Just need a guide on what I should do to fix things or at least more stable