Итак, начнём!

1 .so можно заменить that's why-вот почему (перевод)

2 надо исправить:

-I'm the 9th grade student.

-travelling

-This summer I'll have a lot of time.....

-....I can stay(здесь надо написать где ты хочешь остановиться, предложение незаконченное).............

-In my opinion.......

-не надо писать at this time.......просто This time.......

-Also I have an experience......

Good luck

Hello, Mr. Brown!

My name is Eugene and I’m a 9th grader. I enjoy traveling and playing several sports, because of that I am interested in your summer camp.

This summer I’ll have lots of time on hand, and would like to participate for 3 weeks starting early July. In my opinion, that’s when the weather is best, which it’s highly important for outdoor activities.

I would love to do the adventure workshop, I’ve tried diving last year and really liked it. Also I have some experience in film making, so the film academy workshop sounds quite interesting. I look forward to helping other campers and learning new things .

Best regards,

Eugene.