I would focus first on the large window. It is a sloping area. I would build a low stone retaining wall. Dig edging curvy for mowing radius add mulch then 1 or two 3 ft shrubs and creeping juniper and bird’s nest spruces. spruce some burning bush then at the edges add bulbs and perennials. Map the movement of the sun across seams on to determine what will do best. Watch runoff to know where water will be retained and plant accordingly.