The beginning should be "to you for your act". The end should be "to help".
Student or Learner
Once again I would like to express my deep sense of gratitude to your act of extraordinary generosity and for taking your time out of your busy schedule to help/to helping me out.
I would say that it could be to help. Could it be, please?
OD, you have had the first part of this corrected in another thread. It's going to get very confusing if you keep duplicating sections. Either write your entire letter in the Editing and Writing Topics section and wait for opinions on the whole thing, or make sure that no parts of your letter are duplicated in your many posts in this section.
Remember - if you don't use correct capitalisation, punctuation and spacing, anything you write will be incorrect.