"Fastly" is not a word. The appropriate word to use in place would be quickly."She is doing it quickly" or "She is doing it fast" are both acceptable.
Yes, the phrase 'what they're doing' is grammatically correct. For example: What they're doing is wrong.
The sentence 'A school housed in the church is doing well,' is grammatically correct.
The phrase "How is she doing?" is grammatically correct. It is a common way to inquire about someone's well-being or current status.
The grammatically correct response to "How are you?" is typically "I'm good, thank you," or "I'm doing well, thanks."
No, "hows you" is not grammatically correct. "How are you?" is correct.
Yes, the phrase "as best as possible" is grammatically correct. It is a comparison using the superlative form to indicate doing something to the highest degree achievable.
"Fastly" is not a word. However, "quickly" is a word which you can use. The words "speedily" and "hurriedly" would also work.
Yes, 'for free', is grammatically correct.
"Not like that" can be grammatically correct, depending on the context.
Yes! That is grammatically correct!
This is not grammatically correct. The correct form is 'you do not know', or the abbreviated 'you don't know'.
'What a drunkard you are' is a grammatically correct English sentence.