急な角度の階段って英語でなんて言うの？

"Steep stairs" are stairs that are narrow, and at an steep angle.

If something is 'steep' it means it is at a sharp angle or a very vertical angle So you would say 'Steep stairs'. A set of stairs can also be called a 'staircase'

Example: "Watch out, the steps here are very steep!" or "My grandma's house has steep steps." "Steps" can be used in place of "stairs."

Steep = rising or falling sharply or almost perpendicular. Steep stairs = a staircase which rises sharply.

The stairs are steep. This means that they are uncomfortable for using and it feels like you're going to fall at any point. Here is an example on how to use this in a conversation: A: I'm getting dizzy while climbing these stairs. B: Me too! They're very steep.

As it is not the stairs that are steep, but the staircase, we would say it is the staircase that is steep, or the set of stairs is steep. "I can't climb a steep set of stairs as I am on crutches!"