I hear you on the mint!
Behind the shed is tricky because of the slope. You need a plant that can stabilise the soil and also tolerate partial shade and sun. Alternatively, you would have to build a couple of rows of little terraces and be aware that it will be dry at the top. I ended up with that in my vegetable garden which slopes too and it is on 3 levels and I grow succulents in the top third and vegetables at the bottom. Vegetables failed to thrive on the top but the succulents are happy