I installed the 1.1 Geck, ran it, then I patched it to 1.5.
I can open the DATA, select any mod, then it tells me that the .esp was created in a higher version?
This I do not understand.

Could someone pwease help me?
Thank you.

You installed the FO3 version of the GECK, which is the wrong GECK. You need to download and install the NV version. You can find it http://fallout.gamesas.com/eng/downloads/geck.html.