Most comparative and superlative adverbs are made with more and most.
Could you talk more quietly? (NOT. . . quietlier?)
A few adverbs have comparatives and superlatives with -erand -est. The most common are: fast, soon, early, late, hard, long, well {better, best), far (farther/further, farthest/furthest,), near; and in informal English slow, loud and quick.
Can't you drive any faster?
Can you come earlier?
She sings better than you do.
Talk louder.