Letter To a Sports Club

Dear Sir, or "To whom it may concern," if you don't know whether a man or a woman will receive it.

I have been attending or "going to" which, in my opinion, sounds more natural / common. your fitness club for about 2 years. Unfortunately, I have to inform you (that) I am going to leave the club or "that I'm leaving your club" or "that I am canceling my membership"

I have a bronze card membership, which gives me the ability to attending or "go to" your or "the" club 3 days per week within a half of year for half a year or "for six months". I have been paying $600 for all of the courses. When I read "I have been paying..." it makes me think that you paid $600 every 6 months and that fee includes all the courses. Is that the case? Or do you mean that you paid $600 only once and it included all the courses? If the latter, then I would write "I have paid $600 for all the courses." To try to make it a little clearer, the expression "have been paying" means that you keep doing paying that amount every six months. Also, maybe you mean "classes" when you write "courses". I know it essentially means the same thing but it sounds more common and natural to say "classes" instead here. So an example of this would be a spinning class, or a yoga class, or a Zoomba class, etc. that a gym offers its members for free along with their memberships.

I've really enjoyed being in going to or "working out at" your sports club, because you have the best sports facilities or "facility" if there is only one in the city, your trainers are very qualified and they have always done their job as well as they could. After 2 years, I feel very strong and I'm proud of my body, and it is all thanks to you.

The reason why I want to stop going to the club or "why I want to cancel my membership" is that I have to move to or "that I am moving to" another city due to my new job.

Thank you so much for your work and supporting me throughout all the entire time that I attended or "went to" your club.

Yours faithfully,
Sergei I.

Letter To a Sport Club

Dear Sir/madam,
I have been attended your fitness club for about 2 years. Unfortanutely(unfortunately), I have to inform you that I am going to leave the club.

I have a bronze card membership, which gives me the ability for to attending of the club for 3 days per week within a half of year 6 months. I have been paying $600 for all courses.
I've really enjoyed being in your sports club, because you have the best sport facilities in the city, your trainers are very qualified and they have always done their job as well as they could. After 2 years I feel very strong and I am proud of my body, and it is all thanks to you.
The reason why I want to stop going to the club is that I have to move to another city due to my new job.
Thank you so much for your job and supporting through all the time when I attended your club.

Yours faithfully,
Sergei I.

Letter To a Sport Club

Dear Sir,
I have been attended your fitness club for about 2 years. Unfortanutely Unfortunately, I have to inform you I am going to leave the club.

I have a bronse bronze card membership, which gives me ability for attending of to attend the club 3 days per week within a half of year. I have been paying $600 for all courses.
I've really enjoyed being in your sport club, because you have the best sport facilities in the city,. your Your trainers are very qualified and they have always done their job as well as they could. After 2 years I feel very strong and I proud of my body, and it is all thanks to you.
The reason why I want to stop going to the club is that I have to move to another city due to my new job.
Thank you so much for your job work and supporting through all the time when I attended your club.

Yours faithfully,
Sergei I.

Very good sentence structure. Your sentences are complex and you use a lot of vocabulary. This was a pleasure to read!

Letter To a Sport Club

Dear Sir,
I have been attending your fitness club for about 2 years. Unfortunately, I have to inform you that I am going to leave the club.

I have a bronze card membership, which give me the ability to attend the club 3 days per week within a 6 month period. I have $600 for the course.
I've really enjoyed being in your sports club, because you have the best sports facilities in the city, your trainers are very qualified and they have always done their job as well as they could. After 2 years I feel very strong and I am proud of my body, and it is all thanks to you.
The reason why I want to stop going to the club is that I have to move to another city due to my new job.
Thank you so much for your help and support throughout all the time that I attended your club.

Yours faithfully,
Sergei I.