So I imported it with with the use of the console.
You should have used "importprivkey" in the console. Is that the command you used?
If you did, then you should have seen the total balance displayed by the wallet increase by the amount that you imported.
The problem is now, that I cannot send anything from a public key, that is in the "address" section.
With Bitcoin-Qt, you don't send "from a public key" or "from an address". You send from the wallet. The wallet chooses which of the various unspent outputs that you've received in the past it will spend, you don't get to control that. As long as the total balance increased after your ran importprivkey, then the paper wallet has been imported.
If the total balance did not increase, then it is possible (likely?) that you included the rescan=false parameter. This parameter prevents the wallet from scanning the blockchain looking for your unspent outputs. It allows you to import multiple private keys faster, but then when you are done, you have to run the rescan yourself.