Making offers:
Shall I make some proposals?
Can I give you a hand?
I'll help you, if you like.
Responding to offers:
Yes, that'd be great.
Great, thanks a lot.
Yes, why not.
No, don't worry. Thanks anyway.
Making requests:
Will you organise that?
Could you give me a hand?
Can you do that?
Making suggestion:
Shall we start?
Let's decide who does what.
Why don't we ask him?