請幫忙改此信文化,急!! 謝謝!

To whom it may concern

Re: Volunteer service of Mr xxxx

This is to certify that Mr xxxx, holder of HKID No. Kyyyy, offered his volunteer service in our office in 1999 and 2003. In those periods [or, while he was here], he showed himself to be a very hard-woking, obliging and caring person.

If you require additional information regarding his service, please feel free to contact me at zzzz.

Yours faithfully

唔明你寫咩....中文ok? 下半都明你港咩...旦係上半就..