* I am grateful. This is a good, straightforward translation that captures the feeling.
* I appreciate it. This emphasizes the value of the action you're thanking them for.
* Thank you very much. This is a more formal and emphatic way of saying thank you.
The difference is subtle but important. "Arigato" (ありがとう) is a common and casual "thank you," while "kansha shimasu" is more formal and expresses a deeper sense of gratitude. Adding "-teimasu" (ています) to the verb "kansha suru" (感謝する - to be grateful) indicates a continuous action, signifying an ongoing state of gratitude.