Mailchimp Help (Advice)

I need some advice, I am happy to pay if your suggestion works for me. I will do my own work. I have 22 lists I have imported into Mailchimp that I've sent a few emails from, which are identical. I want to create a master list, but retain the flexibility of having all of my email addresses in their respective target groups. There has to be an easier way to keep these lists individually segmented, but I can send them as a single campaign (or choose to send it to sub-groups from my master list). I've tried lots of stuff, the below makes the most sense... 1. Creating a master list (empty) and importing contacts into a group. First lot of contacts moves into a group, but the second lot of imported contacts is never imported. This shouldn't take a skilled operator more than a few minutes to explain. Payment upon successful work commencing for me, I've tried doing this for 2 hours, getting notwhere!