Learn Spanish (Latin America): Cuanto más usas la mascarilla por la noche, menos quebradizo está. - The more you use the mask at night, the less brittle it is.

In English, we say "The more... the less...". However, in Spanish, proportional comparatives do not use definite articles. You just start directly with cuanto más (or mientras más) and follow up with the second comparative word, like menos. Translating the "the" by saying el cuanto más would be grammatically incorrect.

Can I use mientras más instead of cuanto más in this sentence?

Yes! In Latin America, mientras más is often more common in everyday spoken Spanish than cuanto más. You could perfectly say Mientras más usas la mascarilla por la noche, menos quebradizo está. Both are entirely correct and mean exactly the same thing.

Why is quebradizo masculine if the sentence is talking about la mascarilla?

Quebradizo (brittle) does not describe the mask; it describes what the mask is treating, which is implied by context to be hair (el pelo or el cabello). Because the implied subject is a masculine noun, the adjective takes the masculine form.

Why use está instead of es with quebradizo?

We use está instead of es because the brittleness is being treated as a temporary physical state or condition that changes based on how much you use the mask. If you used es, it would imply the hair is permanently brittle by nature, regardless of the treatment.