Fulfill the law of Christ

We are responsible to others and for ourselves. “Carry each other’s burdens,” says Galatians 6:2, “and in this way you will fulfill the law of Christ.” This verse shows our responsibility to one another.

Hi,

1. I don't understand "reponisble to others" and "for ourselves". When should I use "to" and "for" respectively?

2. What does full the law of Chrise mean?

Thanks