Can anyone help me? Application letter

[Martz]

Thanks in advance to everyone :)

Here's the task:
GLOBAL MUSIC SHOPS

We are looking for people to wotk in our international music shops for three months in the summer.
- Are you interested in music?
- Do you have any useful experience?
- Is your level of English good?
Apply to the manager, Mr Boston.

Dear Mr Boston,
I have seen your advertisement in a magazine, and I am writing to apply for a job in your music shop.
I am a 17-year-old student from Italy, and I have just finished school. I have always had a particular interest in music, especially Jazz. Therefore, I have a fairly good knowledge of it. Besides, I worked in a music shop similar to yours for a year, while studying in high school.
I guess this could be a useful experience. Moreover, since I have good English skills either in writing and speaking I think I meet the requirements for this job.
In fact, I have just taken the Cambridge First Certificate exam, where I was awarded the highest mark.
I attach my resume to prove what is written above.
I look forward to hearing from you.
Yours sincerely,

M.V.

[billmcd]

A few suggestions:

Dear Mr Boston,
I have seen your advertisement in a magazine, and I am writing to apply for a job in your music shop.
I am a 17-year-old student from Italy, and I have just finished school. I have always had a particular interest in music, especially Jazz. Therefore, I have a fairly good knowledge of it. Besides, I worked in a music shop similar to yours for a year, while studying in high school and gained useful knowledge about music and the music-selling business.
I guess this could]be a useful experience. Moreover, since I have good English skills either both in writing and speaking, I thinkam confident that I meet the requirements for this job.
In fact, I have just taken the Cambridge First Certificate exam, where I was awarded the highest mark.
I attach my resume to prove what is written above support my qualifications.
I look forward to hearing from you.
Yours sincerely,

[Martz]

thank you a lot

[Gillnetter]

Thanks in advance to everyone :)

Here's the task:
GLOBAL MUSIC SHOPS

We are looking for people to wotk in our international music shops for three months in the summer.
- Are you interested in music?
- Do you have any useful experience?
- Is your level of English good?
Apply to the manager, Mr Boston.

Dear Mr Boston,
I have seen read your advertisement in a magazine, and I am writing to apply for a job in your music shop.
I am a 17-year-old student from Italy, and I have just finished school. I have always had a particular interest in music, especially Jazz. Therefore, I have a fairly good knowledge of it music. Besides, I worked in a music shop similar to yours for a year, while studying in high school.
I guess this could be a useful experience. Moreover, since I have good English skills either both in writing and speaking I think believe that I meet the requirements for this job.
In fact, I have just taken the Cambridge First Certificate exam, where I was awarded the highest marks.
I attach my resume to prove what is written above.
I look forward to hearing from you.
Yours sincerely,

M.V.

The changes that I have suggested are based on how an employer would consider this letter. You don't have to prove anything at this point - your resume is all that is needed, proof comes later. You shouldn't write "either" when referring to your language ability - "both" is a better option. Just because you like music doesn't mean that you have a deep understanding of it.