Fixing leaky shallow-pitch patio roof?
Your roof is much to shallow (about 2/12) for asphalt shingles which need about a 4/12 pitch.  You need to tear those off and replace with with a membrane or "torch down" roof surface, or possible standing seam steel.

If it's been leaking for any length of time, expect to replace decking, and possibly rafters as well due to rot.