One possible version:
Dear Sir/Madam,
I am writing to you because I am interested in the accommodation you have offered to someone who will help with your two children．I am a twenty-one-year-old boy and I come from China．I have been learning English for several years and apart from it, I can also speak two other languages fluently which are Spanish and French．I once worked in a kindergarten for one year, so I know how to take good care of children．.
I am enquiring about the time needed and when to start．Moreover you have mentioned languages, but I do not know what languages are requested．I would like to know what kind of experience you require for your children, teaching or caring for children．Lastly, I want to know what kind of accommodation it is and how it is like．If I am the right person, please let me know．Hope to receive your letter soon．
Yours faithfully,
Li Hua
略