“Well listen, I'm going to go mingle a bit.”

You're at a party with lots of people. You've been standing and talking with someone for a few minutes, but now you want to end the conversation so that you can talk to other people as well. You say:

 Well listen, I'm going to go mingle a bit.

Well listen, I'm going to (do something)

This is something you can say at the end of a conversation to say what action you're going to take next. Another example is:

Well listen, I'm going to talk with Heather and I'll give you a call by the end of the week to tell you what we've decided.

When you use this phrase in a conversation, you sound like you're confident and in-control.

mingle

To "mingle" means to walk around and talk to a lot of people at a party or event. If you just talk to your friends, or if you're sitting down at the party, it's not mingling. Mingling is when you have lots of short conversations with different people.

a bit

"A bit" means "a short time" or "a small amount". In the example above, "mingle a bit" means "mingle for a little while". The person who said this wants to communicate that she will come back to talk again later.

You can also say "for a bit"