Trying to work out best way to do our deck, without either under or overbuilding, but also avoid any issues, and get around a few challenges in the ground etc.. Ive attached a couple of diagrams. I havnt put posts in diagram, as that is one of the things to determine, is how the red element on one of the walls could be used, and indeed if its permissible to support the beams using it or not, which will effect where the posts need to go. Any help or alternative ideas are welcome. Sketches and some photos below: