When you indicate a manner of doing an action, you use an adverb, not an adjective. (Adjectives are those words which modify nouns and adverbs are words that modify verbs.)

Examples:
I eat really quickly (eat quickly), cf. I am quick (I quick)
We work hard
He drives fast
She drives slowly
They speak English beautifully

However, sense verbs are followed by adjectives:

She feels terrible/good - feel well only refers to health!
He looks good/awful
It smells nice
It tastes bad
It sounds wonderful

Notice this -- these are not sense verbs, so we go back to using adverbs:

She dances terribly
She sings well
She reads carefully
He drives nicely