Dear Mark,
Thank you for your letter. Sorry, i haven't written for a long time, because i was so busy at school.
I think you should tell your friend not to leave litter in the street. There're special rubbish bins, so we can use them. If we want to live in beautiful cities, we should keep streets clean.
As for me and my friends, we don't have many problems. We always try to reach a compromise when we disagree with each other. And we're eco-friendly, we never drop litter in the streets and usually try to sort it.
It's the smallest thing we can do for the environment.
Well, i have to go now. I'm looking forward for your next letter.
Best wishes, *name*