Hi OP,
I'm sorry for your loss. I hope you don't mind if I check that you have claimed Bereavement Support Payment? (assuming you are in the UK). If not consider it as a matter of urgency as the longer you wait the less you can claim and the one year mark makes a difference to that. Don't feel the need to reply I just wanted to make sure you are aware of it.
To help you ease in to cooking I would suggest doing an online shop with a couple of meals in mind but not too much fresh stuff that you will have to chuck if you don't use it.
A big freezer is very useful. If you don't have one we got ours for around £100 from a second hand furniture shop (BHF) and they delivered it for a small fee.
We buy ready cooked chicken pieces
https://www.tesco.com/groceries/en-GB/products/302282232
and they form the basis of
currys (often just fried with an onion adding a jar of curry sauce),
pesto chicken (with jar of pesto/chopped up cherry tomatoes/pine nuts)
sweet and sour chicken (jar of sauce)
Chicken wraps or pittas - with salad/Dips
Chicken fried rice with fried spring onion, chopped peppers/egg/rice.
We use microwave rice most of the time for ease.
We use a bag of frozen mince for bolognaise or cooked up before making into fajitas.
You can use shop bought chopped frozen onion/chopped frozen peppers in these recipes also for ease and no waste.
Shop bought frozen mash is quick and easy. when it is nearly done and stir in a bit of milk and butter. You can keep a bag of frozen sausages such as Richmond skinless sausages for a quick sausage and mash.
Frozen shop bought jacket potatoes. Not cheap at up to £1 each potato but cheaper than take out.
Frozen peas/sweetcorn and green beans all cook up nicely.
A Gammon usually has a use by date of several weeks so when you have more time e.g. the weekend you can put that in the oven and have with jackets and boiled up frozen veg with little work.
Fishfingers/chipshop style fish with oven or air fried chips and peas/bread and butter is a good replacement for a Friday takeaway and will probably add up to about £5 depending on the price of the fish you buy so much cheaper than chippy. We love the Tesco 80p for 10 fish fingers.
Always have pizzas in the freezer for when you don't want to cook. Curly fries and garlic bread slices too if you like them. A home pizza night will cost you £5 -£10 rather than £20++. In the case of pizza kids might enjoy making their own as a weekend activity or adding topping to a basic shop bought one.
Spare loaves of bread in the freezer also saves a trip to the shop.
If you are buying takeaway everyday I would start by planning and aiming to cook one or two nights each week and build it up from there.