Исправьте ошибки, , завтра сдавать. dear sir/madam manager, i saw your advertisement and would like to get a gob as a waitresses at a hotel. it seems to me that i am a good condidature, because i have a lot of experience, i have worked as a waitresses last summer and had a excellent job. also, i am cheerful, sociable and hardworking. i am available for interview on any weekday morning. i am looking for forward to hearing from you. yours fouthfully, helen

I am looking for forward to hearing from you — I am looking (!) forward to hear (какой инг, если инфинитив) from you - две грубые ошибки.
А так все вполне норм)
Ну и запятых много, они там не нужны. Обращение\прощание не в счет, есессна

Dear sir/madam Manager,
I saw your advertisement and  I would like to get a gob as a waitresses in a hotel.
It seems to me that I am good candidature, because I have a lot of experience, I have worked as a waitress last summer and I had an excellent job. Also, I am cheerful, sociable and hardworking. I am available for interview on any weekday morning.
I am looking forward to hear from you.
Yours faithfully,
Helen