Can I create a 3D model in QGIS or is there some model for 3D city models? I need these information for my project.
There is QGIS Globe. You'll need to run QGIS on Linux though (Source http://sourcepole.ch/the-state-of-qgis-globe).
To see QGIS Globe with PostGIS 3D in action check http://vimeo.com/54776907.