How to express the willingness to help others

[sisimango]

When I want to say sth like "whatever you need just let me know and I will try to help you."
How can I express it properly and idiomatically?:shock:

 

[tedtmc]

Why does it have to be idiomatical?
I thought the idea is for the message to be simple, clear and polite.

If you need any help, do let me know. I'd be glad to help.

not a teacher