Conclusion: The conclusion below the text. Always use your sincerity, your past or yours or your truth, your truth, etc. Signature: the sender's signature, written at the bottom of the conclusion.
The writing template of English suggestion letter is as follows:
Dear _ _ _ _ (recipient's name),
I am glad to receive the letter you sent me years ago. I've been thinking about the question you asked me.
In my opinion, you should _ _ (suggestion 1). One reason, _ _ _ (reason 1). There is another reason, I think _ _ _ (reason 2). There, I think it's a good idea for you to _ _ _ _ (suggestion 2). What are you waiting for?
You are sincere,
_ _ _ _ (author's name)
Dear _ _ _ _ (recipient's name):
I am very glad to receive your letter to me _ _ _ years ago. I've been thinking about the question you asked me.
In my opinion, you should _ _ (suggestion 1). The first reason is _ _ _ _ (reason 1). Another reason, I think, is _ _ _ _ (reason 2). So, I think you'd better go to _ _ _ _ (suggestion 2). What are you waiting for?
Yours respectfully/sincerely
_ _ _ _ (author's name)