Thanks a lot for sharing your expertise and your clarification on castellano and español.
For some reason I thought that mainland Spanish is called castellano and including all it's semi-offsprings throughout the world, generally, it's español. But it was probably just our teacher, who happened to insist on speaking only Spanish during the lessons the whole time from the very beginning, so for quite some time (as complete beginners) we had some
minor problems decyphering some explanations. Thank God I knew some French otherwise I could have gotten a nervous breakdown sometimes ...
Gracias de nuevo.