I'm sorry to hear that. Hopefully sleep will get better once the girls get a few months older.

Here are my 2c:

Just focus on cooking from wholesome ingredients. Don't try to get into very complicated diets or very complicated recipes.

Just cook basic, wholesome meals for some time and once you get the hang of it and sleep gets better you can start digging deeper into more elaborate meals or diets.

And walk / exercise every day.