"Preparing correspondences" could be a grammatically correct phrase, but it would be fairly unusual. This phrase would be appropriate only if the entity modified by the phrase is actually engaged in two or more different correspondences at the same time. For example, "Those four clerks are engaged in preparing correspondences with all of our ambassadors." For a single person to be preparing "correspondences", she would have to be writing or typing at least two different messages over the same time period, and this is not the way most people work. Under most circumstances, the singular "correspondence" is considered a collective noun that can include more than one individual message.
Yes, 'for free', is grammatically correct.
The phrase "how don't I" is not grammatically correct. A more correct way to phrase it would be "why don't I."
This is not grammatically correct. The correct form is 'you do not know', or the abbreviated 'you don't know'.
Yes
The phrase "Is you don't miss me do you" is not grammatically correct. It should be rephrased to something like "Don't you miss me?" to be correct.
The phrase "had already left" is grammatically correct. The phrase "had already been gone" is not grammatically correct.
yes, it is
No, it is not grammatically correct to say "keep stick to." The correct phrase would be "keep sticking to" or "stick to."
Yes. It is a noun phrase.
The correct phrase is "that was you," as the verb "was" agrees with the singular subject "you."
Yes, it is grammatically correct. "Part and parcel" is a phrase that originated as a legal term in the fifteenth century. It means an essential or integral part.
Yes, the phrase "I came home at about one o'clock" is grammatically correct. It follows a subject-verb-object structure and conveys a clear message about the time of arrival.