The wall and the fence need treating with a quat ammonia based chemical, hypo on the wall will spill all over the decking so you need to do that as well same goes for the fence, hypo will mark the fence and the pathway.
It’s not a customer who wants to see instant result before they hand over the money it’s for your girlfriend. The best (but not quickest) solution is quats, it will also have a residual effect it will stay clean for longer.... with hypo they moment your rinse if off it stops working.