First, decide if you want to write a formal letter or an informal letter. If you don't know the person you are writing to, or if you are writing for a professional or academic reason, you will probably want to write a formal letter. If you know the person well, and you are writing to them for a personal reason, you can write an informal letter.
Here are some tips for writing a letter in English:
Start with a greeting, such as "Dear" followed by the person's name, or "Hi" if you know the person well.
Write your letter in clear, concise sentences. If you are writing a formal letter, avoid contractions (don't, can't, won't, etc.).
Make sure the letter is well-organized, with each paragraph discussing one main idea.
If you are writing a business letter, use a professional tone and avoid using slang or jargon.
Conclude your letter with a sign-off such as "Sincerely," "Best regards," or "Take care."