If you want to use the freeware scenery Denmark Scenery v1.4 together with Vidan Designs Sonderborg X, you will need to deselect "Soenderborg Airport (EKSB)" during the installation of Denmark Scenery 1. 4
If you have already installed Denmark Scenery 1.4, you will need to uninstall it.
To uninstall Denmark Scenery 1.4, run the installer again and select “Remove” (or use the Windows Control Panel Add/remove programs).
Then reinstall Denmark Scenery 1.4 and during the installation, choose "Custom setup". Here you will have the opportunity to disable various elements of the scenery, including airports and airfields.
Make sure that you under "Soenderborg Airport (EKSB)" selects the option “Intire feature will be unavailable”, like on this image: