Is gaining more points any use after reaching level 25?
Gaining points isn't really any use before getting to level twenty five.
Gaining points is of use before level twenty-five, because it allows raising levels, which gives lingots, which are needed to take quizzes to test progress.
How long did it take you to get so high in French and Spanish? Did you know much of those languages already?
I knew some French and almost no Spanish. It took me maybe six months to get to level twenty five in them, the vast majority of my points come from immersion though.
Have you completed the trees?
Sorry, I can't respond to your other comment directly. I actually haven't finished the trees yet.