A few years ago I installed a patio off of our house with retaining walls on two sides for privacy (see images below). However, in recent winters the corner where the walls meet have started to separate as shown in the pictures. So far, the walls do settle back into position in the spring time but I am worried about the long term consequences of this movement and the possibility that the gravel/sand foundation is being washed away. I am confident this has to do with poor drainage and possibly a poor foundation (gravel and sand, rather than cement) but I am hopeful that someone here could provide some advice on how to remedy this issue without starting over from scratch. I'm curious if installing a dry well or putting a waterproof membrane around the patio would remedy or mitigate this issue. I would really appreciate any advice I can get on this topic. Thank You

So, we just bought a foreclosure that was flipped (maybe 10 years ago?), and it was done poorly. The one surprise we found so far, is that the concrete driveway that extends along the whole N side of the house must have been at a much lower grade in the past. There were two walkout basement doors on this side which have been framed in with wood and wood siding and then the grade of the driveway raised above the basement floor level and a cement slab installed. Obviously, the couple feet below grade rotted and is a pile of mush that we found when we removed the paneling in the basement. I've attached a drawing that explains that corner of the house. The grade of the driveway needs to be raised for better drainage, so the windows mentioned will be below the new grade at the bottom, and we'll be putting in a flower bed instead of cement right up to the house. I assume everything below grade needs to be filled with cement block tied to the existing block walls, which we'll do ourselves. My question is, what's exactly holding the house up, and how to we accommodate that as we do the work? There must be some serious headers (right word?) above these huge gaps in block, and a post of some kind in the corner indicate between the windows... I hope the 2x4 framing and windows aren't holding the upper floor up?? My questions are, what procedure should we use for safely tying in cement block without letting the house fall down? Assuming we leave the corner windows in place, what should be holding that corner up between them? Any suggestions about the design of what we put in place? I think I understand about the basics of filling in a gap in a block wall, with wall ties. I'm more concerned about the structural integrity and design, and the order of steps. Anything would be helpful! :)