關于英文?

Use online msn distionaries, you can check the meaning of each wording and listen the pronounication.

==> you should not use "it" , because it is " someone" do.
== > need to == must have to , the later sounds more polite
==> Should +subject + verb==> more polite and invitation other give comment

Should we do sth?
We must have do do sth,don't we?

Is it necessary for us to do that?
Must we have to do sth?
( The latter two questions==> Gamma is acceptance, but this is not the native English way of speaking)