.Dear Sir or Madam,
I am writing in connection with your advertisement [You need to state what the advertisement was for: "...your advertisement for adventure courses"/"...your advertisement for an assistant"...] which I saw in the latest "Traveling" magazine. I would like to try climbing during summertime and I prefer to travel by bus.
Firstly, I would be grateful to know how many days courses usually take. I am keen on swimming. Is it possible to do more than one activity on my course? I mean I would like to do climbing on the mountains and swimming in the sea as well.
Secondly, I would rather stay in apartments. Could you please send me more information how well the apartments are equipped . Is it necessary to pay some extra money for using a microwave oven or for anything else?
Lastly, I would like to improve my English. The best idea for me would be intensive individual lessons which focus on speaking and writing.
I look forward to hearing from you soon.