Demented Dungeons help!

[Tazz]

Hey all out there.

I just munchkin 6 - demented dungeons, and sittng here ready to play it with my gf.

We are having a hard time understanding the rules clearly, so hope some of you guys and girls can help explain it. The rules feel kinda not clear everywhere and we aint really sure about some of the stuff.

We are not native english speakers so we have some troubles with the rules.

We understand that all in the group are in the same dungoen in the start. But afterwards how is it? The rules says: While a dungeon card is in play, it affects all.
But later in the rules it says that you can choose to stay in a dungeon and so on. We are not sure if you allways are in the same dungeon as the other players, or that you are all in diffrent dungoens after the first one.
Futhermore, if my gf wants to be in the same dungoen as i ended up in, how can she join the dungoen im in?

In short words. Can someone explain dungeons rules etc, to someone that how trouble with the officale rules.