is this letter correct?
Dear sir,
I'm sending you my medical certificate attested by UAE Embassy from Colombo that you have requested. I'm sure this will be useful to carry on your further work on getting my visa. I'm expecting your good reply as soon as possible.

Thank you.

If there is a good method to write this please mention it.

Thank you.

Question

is this letter correct?
Dear sir, 
I'm sending you my medical certificate attested by UAE Embassy from Colombo that you have requested. I'm sure this will be useful to carry on your further work on getting my visa. I'm expecting your good reply as soon as possible.

Thank you.

If there is a good method to write this please mention it.

Thank you.

Answer

Dear Sir,

Thank you for your letter of [1st April] about my application for a visa [reference xxxx].  As requested, I enclose my medical certificate attested by the UAE Embassy at Colombo.   [[ Please let me know when you will be able to issue the visa. ]]

Yours sincerely,
....

The last sentence is probably unnecessary --- unless you know it will be a long time.  However, you do need to include the reference number of your application --- or the equivalent.