Hello. Bakit kaya ayaw mag sync ng facebook ko sa calendar? Pag nag log in ako sabi login failed try again. Thanks

Bear in mind I am not extremely tech savy. I just got an S5 when the S6 came out, AT&T, and I don't know if it is just my phone, if I've done something wrong. What I'm trying to figure out is, why when I am in Facebook it will freeze and occasionally close?