I think the OP rather meant "DEUXIÈME" (second) here.
And if it's an American second floor, it would be "le premier étage" in Europe

Clever ! It's also logical : chambre 201.

Ah yes indeed. Thank you!

Merci beaucoup ! I find that many language resources do not spend enough time drilling the pronouns  “y” and “en”, or teach it way too late as an “advanced” topic even though they seem to be used in very basic conversation.

Je t'en prie.
These pronouns are super common, so yes, they should at least be introduced quite early in the authentic material. Maybe they come late because teachers need to introduce other notions first? Like for exemple, enough verbes with "de" and "à", the "partitifs"...
On this website I found two mind-maps (one for each pronoun) that seem quite useful: https://nathaliefle.com/pronoms-en-y-confusions/

Thank you so much, I'll check it out! I agree it's tricky. The other interesting problem I've noticed for me at least is that, even when I consciously grasp the grammar of a phrase like "On en a une," or "Je viens d'en partir," often it still won't have that intuitive meaning we're trying to acquire, which seems to only come with a ton of practice.

When written, these two words seem to be very important, while when spoken they can sometimes almost go unnoticed. I'm sure that when I speak I can say "On n' a une" and "Je viens d'partir" So it does not help to acquire it if you cannot hear it!

Maybe it will start to stick at the moment you learn the most common sentences almost like idioms : "J'y vais" (because "je vais" does not really exists, so it will always be "j'y vais"), "Qu'est-ce que tu en penses ?" (more common as Qu'est-ce que tu penses ?)...