DEAR MR SMIT
I am writing to ask for more information about your holiday camp.I am interested in your offer but i need some details.
Firstly i wonder what accommodation is suitable.Could you please tell me about the sort of conditions on the holiday.
I would be grateful if you could tell me more information about health and accident insurance about is it safe at all.
Secondly could you please tell me about baggage.Is there any weight limit.Also I want to know about hotel romms are they double or single.
Finally i wonder is it all right if i bring my dog with me ?
Send me more details about the price.
I am looking forward to hearing from you.
Your sincerely
Elena Ivanova.
Hi Anon,

Work on your word order when you want to ask a question and don't forget the capital "I", also on the selection of the words:

Finally, I wonder whether/if it is all right if I/to bring my dog with me ?

Secondly, could you please tell me about baggage weight limit? / Secondly, is there any limitation on the baggage weight?

Also I want to know about hotel rooms if they are double or single. / I'd like to know if the rooms are double or single.

Mind you, I'm not a native!
DEAR MR SMIT
I am writing to ask for more information about your holiday camp.I am interested in your offer but i need some details.
Firstly i wonder what accommodation is suitable.Could you please tell me about the sort of conditions on the holiday.
I would be grateful if you could tell me more information about health and accident insurance about is it safe at all.
Secondly could you please tell me about baggage.Is there any weight limit.Also I want to know about hotel rooms are they double or single.
Finally i wonder is it all right if i bring my dog with me ?
Send me more details about the price.
I am looking forward to hearing from you.
Your sincerely
Elena Ivanova.

personnaly i didnt find serious Mistakes in your Letter it is good and of course if you take in consideration the correction that Languagelover added ,

and i guess it's late to wish Good luck in the exam.