Is a congruent angle always 90 degrees?

There's no such thing as "a congruent angle". "Congruent" is a comparison

between two or more angles. Whenever you see the Word "congruent" the

Words "to each other" should also be there. If one or more things are the

same size and shape, then they're congruent (to each other), no matter

what size they are. All 90-degree angles are congruent (to each other),

because they're all 90 degrees. All 7-degree angles are also congruent

(to each other), because they're all 7 degrees.

A congruent angel presumably has two wings of exactly the same size and shape.