pls check mistakes for formal letter

[kohieutaisao]

Anyone can check mistake for me pls......it's really urgent.This is formal letter i send to another company to refuse their proposal .

Dear Mr.S,
Thank you for your letter of August 24th .I really appreciate for your cooperation and valuable suggestion in serving flights of VietNam Airlines.
As your proposal that we should temporarily stop carrying out SLA ( Service Level Agreement) during period time of operating new terminal T2.After careful consideration and following the direction of Deputy Director of Service, we suggest that both of Tiags and Occ should still maintain assessment and measurement all standards undertaken.
It is not really so important to achieve the current target, furthermore the information we get from SLA is foundation for us to know how much we succeed in applying SLA for new terminal T2. Moreover, this is also basic for us to adjust measurement tool for SLA in furure.
We hope to have futher cooperation with your company in the future.We wish health and success to you and your staves.Thank you

If it's convenient, can u supply for me some best wishes sentences at the end of the letter.And furthermore can u help me to write letter as English formal style? Actually it's letter i translate from Vietnamese to English.And i feel there r sth not natural^ ^.Thanks