mittlerweile in English:

You go and walk the dog and meanwhile I'll clean his basket out.

I suggest you try and forget about your recent problems and in the meanwhile drink less coffee and try to get to bed earlier.

A lot has changed meanwhile.

Meanwhile, the foolish uncle was sitting in the living room.

Meanwhile, the PIRATE Party offers space on an internet server of their own to all CDU groups in Kassel that are affected by censorship by the party leaders.