I have received some files from our external design office with the extension .nwc and .dgn (software: Autodesk Naviswork) and I cannot used it in my Autodesk Inventor Professional 2011 (Error: "Failed to open document"). They cannot export in step file or others which can be useful for me.
There are two Autodesk softwares and we cannot use data in both???
Navisworks files do not work like that. You cannot use that data in Inventor, and trust me, you don't want to anyway. The files are probably comglomerated with other data already that could choke any 3D modeler, not just Inventor. If you want to view these files and navigat them, then download the Navisworks Freedom view to at least see what is in them.
This user of Navisworks you are getting files from already has some other modeling files they brought into Navisworks, they need to send those files to you in a way to can read them, not the ones they sent you. Navisworks doesn't create the geometry, it puts it together.