Do you have a specific question about one of these answers?
At any rate, here are some corrections at a glance:
A) "To be done for = to be doomed"
B) "I could do with a drink. = I would like a drink."
E) "I simply can't do without it. = I need it."
H) "to do someone in ≠ to kill hilariously" It just means to kill someone. There's nothing funny about it.
"Handsome is as handsome does." -- It's not just about how you look, but how you act.
"Cut your cloak according to your cloth." -- Make sure your goals match your means.
"His wife wears the trousers." -- His wife makes all the important decisions.
"Too big for one's boots." -- We say this of people who overestimate their abilities.
Some of those uses of "do" are BrE, which I won't comment on.