Translation of Nachhilfe

I try to learn English as much as possible so that I can travel next year to the United States. I would agree to your proposal but I also need to find good teachers. My goal is quality and speed.
Anyway, there are a lot of people on board and I no matter how high the waves may be, I always suffer from nausea or seasickness. I have not been on a small boat before. I will have to vomit.
I'd be very happy if you could correct my Spanish. In return, I'll help you too, of course. 3 years ago I traveled to Chile to visit the country, only for a month, unfortunately. Loved the Cordillera!