Complex sentence: Her father is the only one that can work but has a very hard time doing so due to a leg injury and severe cough, he has suffered from since the school he was teaching in was bombed.
Split into simpler sentences: Her father is the only one who has the right to work in the family but he has a very hard time doing so because of a leg that was injured in a bombing. He also suffers from a severe cough, which developed after the school he was teaching in was bombed.