Hello. I'll be very grateful for your help.

1)Is it possible to say "I'll answer your question if you are insisting" or is it "if you insist"?
2)Is the sentence correct "By the time you come, the letter will be ready" or is it "when you come"?
3)Which tense is correct or better (Perfect or Simple) in the context "The letter has been written / is written. You can post it"?
Thank you for all your help.

1. "if you insist" is the phrasing used.

2. Your first sentence is very good. The second phrasing is OK, but the first is better.

3. I'd use "has been written."

Hello! I'll be happy to assist you with your questions.

1) The correct phrase to use is "if you insist". The word "insist" means to demand, assert, or persist in a particular course of action. So, when someone insists on something, it implies a stronger level of determination. Therefore, we usually use "if you insist" to convey that we will do something in response to their firm request or demand.

2) Both sentences are grammatically correct, but they have slightly different meanings. "By the time you come, the letter will be ready" implies that the letter will be ready before the time of your arrival. It emphasizes the completion of the letter before you come. On the other hand, "When you come, the letter will be ready" simply suggests that the letter will be ready at the moment of your arrival. It focuses on the coincidence of your coming and the letter's readiness.

3) Both tenses can be correct, but the choice depends on the specific context and intended meaning.

- Using the present perfect tense, "The letter has been written. You can post it," suggests that the action of writing the letter has recently been completed. It implies that the writing process is now finished, and the letter is ready to be posted.

- On the other hand, using the simple present tense, "The letter is written. You can post it," conveys a general statement about the status of the letter. It suggests that the letter is currently in a written state and can be posted.

Both options can be suitable depending on the context you wish to express. If you want to emphasize the recent completion of the writing process, you can use the present perfect tense. If you want to focus on the current state of the letter, you can use the simple present tense.

I hope this explanation helps! Let me know if you have any further questions.