Mehdi, here are the meanings you are looking for the below sentences:

I am looking for these sentences mean ;
Do you mean it ? -- This means just what it says, "do you mean what you say or do, or etc.."
The more the merrier -- This means 'the more the better (in a happy way)'
Comer -- never heard of this one
go off around -- never heard of this one
you could fall over --
assitant entertainment director
eye-opening -- This refers to something that makes you think twice about things next time;
hot lowland plains
nothing exciting!