Since when does peeling and cooking potatoes take more than half an hour, unless you are baking or roasting them in the oven? Even less than 10 minutes if you have a microwave :dunno:
I suggest you buy a basic cookbook
You do realise you can buy loose potatoes, or small bags of them, not just 5 or 10kg bags?
Buy smaller amounts of fresh fruit and veg each time and they won't go off. Cauli and pumpkin are two that keep really well.
When I buy frozen veg I buy them as separate bags eg a bag of peas, a bag of corn, a bag of beans etc, rather than a bag of mixed veg as the flavour in the mixed ones comes out pretty tasteless and nothing like the real thing.
Fish, like humans, like variety in their diet so experiment.