Dear [имя],
Thank you for your letter. Sorry I've not written for so long, I was helping my granny in the countryside and staff.
First of all, snowboarding is an extreme sport, so you have to be careful. Besides, keep all the necessary equipment with you in order to not get hurt. What is more, I would join a gym if I were you.
By the way, recently I've visited a skating rink. I had never been on a skating rink before. I am used to roller-skating in summer, but skating is yet difficult for me and I've got much to learn until I can say that I am good at skating.
Look forward to receiving your reply.
Best wishes,
[имя]