* "resolveing" should be "resolving"
* "ina" should be "in a"
* "maNNER" should be "manner"
Here's the corrected sentence:
Thanks for resolving the matter in a timely manner.
Additionally, you could improve the sentence by adding a comma after "thanks" and making it more formal by using "Thank you" instead of "Thanks."
Thank you for resolving the matter in a timely manner.