Dear Mr. Brown,
In response to your advertisement, I am writing to apply for the position of shop assistant.
I am very hard-working and reliable. In addition, I worked as a shop assistant in a sports shop last summer and in a music shop two years ago.
My English is fluent and I can speak a little German. I am good at working with other people and I am a fast learner.
I hope you will consider my application favorably. Enclosed is my résumé, and I would be happy to attend an interview at a time that is convenient for you. Please do not hesitate to contact me if you require any further information.
I look forward to hearing from you in the near future.