Sep 20 - A mistake in a paragraph and how to fix it

I sent my brothers girlfriend who is Mexican a Spanish paragraph,She said it was good except I didn't use the word "to" I used que which I thought also meant "to" but she said to use "a". The paragraph is copied and pasted below My question is when should I use "a" and when should I use "que"?

Yo creo lo que paso con él y su esposa no tiene nada que hacer con su trabajo,porque el trabajo y su casa son dos lugares differentes.