Original sounds disappeared.

And the new sounds I try to assign from Halion Symphonic Orchestra just sounds like crap. CRAAAAAP.

So please if someone can help me bring back the initial sounds. plz. How to? It’s violin 1 and 2, viola and cello.

Ok, just found out myself.

Another question: When violin 1 and 2 play the same note dorico makes one of them and octave higher. Why? Can I avoid it?

Try doing Play > Apply Default Playback Template to put things back to their defaults.