If you would like to thank someone for helping you, here is a simple template you can use to write a letter of appreciation for help and support.
You came out of your way to help me and for that, thank you! I can’t say enough words to show how much I appreciated your kind gesture. You’re a blessing in disguise if there ever was one. I know that you are a busy person but you helped me anyway. It took a lot of effort to do what you just did.
Don’t think that I am somebody who will forget what you just did. I am someone who shows gratitude to kind people. I will definitely return the favor when you need my help. Just tell me when the opportunity arises and I will be there.