French language Q&A Forum

In writing French, when do you use "on" and when do you use "nous" ?

I'm inferring from the context that "clou" here means something like "highlight" or perhaps "grand finale", but I was unable to anything like this sense in the reference materials that I have on hand. "The nail of this stay" doesn't make a lot of sense to me, so I figure it has to mean something else.

Help in sorting this out will be appreciated.

I don't understand the grammar of parmi lesquels choisir in this sentence. could anyone help to explain? thanks. 

I'm learning to play the guitar. 

J'apprends à jouer de la guitare.

It's quite difficult because I'm a bit old to start [learning] an instrument. 

C'est assez difficile parce que je suis un peu vieux pour commencer à apprendre un instrument.

I'm happy with my progress, and I hope to continue like this!

Je suis content de mes progrès, et j'espère continuer comme ça !

Can you tell me

1)Difference between 'une cour de basketball' et 'un terrain de basketball'

Merci

Is the sentence "Il s'est excusé pour n'apporter pas ses lunettes" a correct translation of the sentence above, if not, what is the correct one?