So youbwantbquick healthy food and, I assume, you are happy with quite simple food (based on fact you eat toast and get overwhelmed?)
Start small. 2 obvious options are pasta dishes and v basic grilled/fried things with veggies. Eg spaghetti bolognaise is simple although does need an hour to simmer, and adding additional veg with the onions such as chopped peppers, chopped mushrooms etc is easy. Also, a packet of mince would do a fee meals so you could have spaghetti bolognaise on day 1, then give yourself a break with mince on toast on day 2! Then freeze the other two or three portions for the following week.
Grilled sausages with mashed potatoes and frozen peas is v simple, quick and again, for a single person one night cooking could do 2-3 days.
Do an online shop rather than in person if it overwhelms you. Stock up on things like frozen veg which can easily be microwaved and add a quick bit of nutrition to whatever you eat. Peas, carrots, beans, cauliflower all good.
What about soup? A pot of soup made in day 1 would feed you for a few days and/or give you individual portions you could freeze? Again, easy, nutritious ans v simple.
Certain veg lend themselves to easy pasta dishes. Tomatoes, obviously. But also courgettes, aubergines, spinach, leeks, peas, with or without small amounts of meat.
Do you like smoked.salmon or.smoked.mackerel? Salmon is expensive but a small portion with scrambled eggs is nicer (mil adds corn, which i find weird but kids love). I had smoked mackerel for lunch this week with boiled new potatoes and broccoli.