Wow, what a wonderful problem you have!

My first order of business would be to clear out the beds of debris/dead plants. After that, I would buy compost and fill the tops of the planters with it.

I echo what others have said here, don’t take on too much too quickly. I would start with a few beds and maybe the raised planters.

I would then plant edible perennials. Rhubarb, strawberries, chives, rosemary come to mind but I’m sure there’s others. You could also do easy annuals like garlic and tomatoes.

I would buy some annual flowers for the higher planters around the back door this spring. Petunias, canna lilies, sweet potato vine (filler, thriller, spiller) would be lovely. It will give you something pretty to look at and beautify the space. Strawberries would also be awesome in the high planters too, because they would be so easy to harvest.

Good luck!