My dad is banging the wall in anger over something I don't know of. My mom says she doesn't know but I think she is lying. What do I do?

First, know that you are not to blame for his anger. Second try to find a quiet place and breathe. At times, when we are in the midst of tension/chaos, we begin to feel overwhelmed. Try to find an outlet - a book or music, etc. - for the mean time and then you can try talking to your dad or both parents when things have cooled down. Your mom may not know what your father is angry about or perhaps she doesn't want to bring it up in that moment. You can try communicating and expressing your concern when things have cooled down.