Rick, you are doing well with damping exercise. It really does get easier with some practice, as you said. The most difficult part is planting 'm' finger on string while plucking with 'a'.
For the speed exercise, I would suggest slightly slower tempo, as you do have some trouble after sextuplets. I think we're supposed to post both exercises 105 and 106. Also make note of the crescendo dynamic indications.
I'm also having constant trouble with my 'a' finger nail. It hooks slightly to the right of center, especially when the weather gets dry. Nail hardener helps with that, but the tone will suffer, so I only use it when I really have to nowadays. What helps a little is leaving the right side longer (i.e. a ramp) instead of a round form, as it will make the hook near the middle less pronounced. But I too need to file often (and carefully!).
Esteban, you are making good progress with "Vaghe bellezze..."! I agree with Rick's comments. You seem to strum a lot with your thumb (in places other than those marked with the vertical wavy line). Although it sounds nice when playing slowly, you should aim for "Andante" tempo, as indicated in the score, and I don't think strumming the eighth notes (quavers) is feasible at that tempo.
This is the only English-Spanish music dictionary that I know of: http://www.dmcclure.org/voc-mus.htm
Unfortunately it doesn't have anything specific to the guitar. You can also use Spanish words in place of English ones when you don't know a word. We'll most likely understand what you mean.