I wrote a sentence,but my teacher said it was wrong.Can you tell me why?Thank you! The sentence I wrote was: This is the first time for me to visit London. And how about this sentence: This is my first time to visit London.
I'm afraid both your sentences are wrong. You can say, "This is the first time I've visited London" or "I'm visiting London for the first time."
I suppose you could also say, "This is my first time visiting London."