Perfect! Thank you guys again for the help.

Yes, the sandbox tools would be the "native" way to do it (although those are actually plugins themselves, too). If you are in to such curvy modelling; it has never been easy with simple SU tools. Either you need to "hand stitch" the curves from endpoint to endpoint (often triangulated) or use different trick of autofolding or intersecting faces... It is not the best thing to try these techniques (while learning) on a real model you are working on but if you can separate individual examples (preferably simple ones from scratch), we can go through a couple of tips and tricks. And there are of course those different, marvellous plugins nowadays. Go to the Plugins subforum under Resources and check out one of the sticky posts: "Plugin index" (or what). Search for loft-ing, skin-ning etc.

Great advice... There nobody left in my office so it's really about time to head back home-> where SU is all about fun I will first learn it the hard way and come back for plugin advice...but it's written down in my list for wanted plugin. Have a nice day/evening

Will it be the same on the other side, too? In that case, just delete the line I drew in the middle and instead of selecting that curve, select the whole middle face with a single (or double) click before running the tool.