Appreciation Letter

[dawoodusmani]

Hi dear teachers!
I've written an appreciation letter for one of my subordinates, who is in charge, for her good performance throughout the year.Can you please check if there's an error here. Please correct if there's one. Thanks a million!
Dear XYZ,
I would like to take this opportunity to express my heartfelt thanks to you for active participation in development, betterment and healthy growth of Yaqeen Education Foundation.
Your enthusiasm and your ability to motivate your subordinates/staff has resulted in a significant increase in productivity, profitability and stability.
I ,on behalf of all members of Yaqeen Education Foundation, wholeheartedly appreciate all your help, efforts and good performance and hope you would continue with the same.

Very sincerely
ABCD

[Tdol]

I'd say:
for active participation in development,= for your active participation in the development,
wholeheartedly appreciate- wholeheartedly thank you for
hope you would- hope you will

[dawoodusmani]

Thanks for your answer. But I doubt that the verb "has" is wrongly used here because the subject is two things; (1) your enthusiasm (2) your ability. Thus it should be the plural. shouldn't it?
Regards!
Dawood

[heidita]

Tdol, shouldn't it be "improvement" instead of betterment? I am not familiar with that expression.

I have just had a look at it is apparently used in finance. Can it be used here?