Qual è la differenza tra We were at the concert last night. (Nosotros estuvimos en el concierto anoche.) e We were in the concert last night. (Nosotros estuvimos en el concierto anoche.)? ?Sentiti libero di rispondere con un esempio.

Well, the preposition «en» has lots of meanings in English.

• It can mean “In”

-> Mi laptop está en mi bolso.
My laptop is in my bag.

• It can mean “on”

-> Los platos están en la mesa.
The plates are on the table.

• It can sometimes mean “at”

-> Estoy en el restaurante.
I'm at the restaurant.

• And sometimes, it can be translated as “by.”

-> Viaje en avión.
I travelled by plane.


So, yes, in the examples you’ve provided, “en” could be translated as both “in” and “at.” I don't know if there's is a difference between “in the concert” and “at the concert,” since my native language is Spanish, and Spanish uses the same preposition for both, then both English sentences mean the same to me.

Tip: don't bother learning what prepositions “mean” because they don't have meanings. They don't have actual translations. Every language uses prepositions differently, as you can see from the examples I gave you.