Я не знаю как начать письмо конечно, но можно написать что-то типа:
Hello,I also have some free time in summer holidays. I go to holidays to the city.And I have hobby for that time. I ride a bike or do some exersize. I do it becouse it healthy and if I do it I be stronger. I don"t need a lot of time to do it. I do it when I have time. These sports you can do with friends. You can do a competitions, and if you train you can win it. It is very interesting and funny. You should to do it