When someone given you some information you can say comment or reply:

Oh, I see.
That’s interesting.
Thanks for letting me know.

If someone asks you for information you can reply:

As far as I know, …
Well, (in confidence,) I can tell you that…
I’m afraid I don’t know.
I’ve no idea, I’m afraid.
I don’t have that information available just now. Can I call you back?
I’m not sure. I’ll have to find out. Can I let you know tomorrow?
I’m afraid I can’t tell you that. It’s confidential¹.

If you want to give someone some information you can say:

I’d like you to know that…
I think you should know that…
Did you know that…?

Or you can write:

We should like to inform you that…
Here is the information you requested…

If someone hasn’t given you enough information you can say:

Could you tell me dome² more about…?
I’d like some more information about…
I’d also like to know…
When/ How much/ Why exactly…?
There’s something else I’d like to know…
Can you give me some more details about…?