grateful letter

Hello, I need to write a note of thanks for my work colleagues. They are chinese people and a little bit older than me. So I want to write it in chinese and wothout mistakes. But I don`t know how to say in chinese following frases:
It was great (nice) to work with you.     跟你们合作是一件很愉快的事。
Thank you for all your help.           对于你们的帮助，我非常感谢。
Thank you for comprehension (understanding).    谢谢/感谢您们的理解
Thank you for make available to work with you.     感谢你们给了跟你们一起合作的机会。/感谢你们让我们一起合作成为可能。
You were very kind.      你们非常友善
Thank you for all.     感谢所有的一切
I don`t forget this a learning experience (worthwhile experiment).   我不会忘记这些学习经历（宝贵的实践）

It would be great if you will help me ^_^