Adverbs are used to modify verbs, adjectives or other adverbs:
My mother speaks quietly. (adverb used to modify verb)
They moved slowly. (adverb used to modify verb)
Their house was extremely expensive. (adverb used to modify adjective)
The cat ran incredibly quickly. (adverb used to modify other adverbs)
Some verbs can only be used with adjectives, others might change their meaning when used with an adverb.
verb used with an adjective used with an adverb look look good (= appearance) look well (= have a good sense of sight) feel feel good (= state of health/mind) feel well (= have a good sense of touch) smell smell good (= odour) smell well (= have a good sense of smell) taste taste good (= preference) taste well (= have a good sense of taste)
Hard and hardly are completely different. Hardly means very little, almost not.
She hardly tried to get the job. (she tried very little)
She tried hard to get the job. (she tried a lot)
Hard means not easy, requiring great physical or mental effort to accomplish and can be both an adjective or an adverb:
Andy is a hard worker. (adjective)
Andy works hard. (adverb)
Some adverbs are formed from an adjective plus -ly: happy – happily. However, when an adjective already ends in -ly ( daily, kindly, lonely etc) we don´t add -ly to it to make an adverb. Instead we use a prepositional phrase with “ manner” or “way”.
When he saw me he started waving his arms around in a lively way and then ran across the road.
She turned and smiled at me in a friendly way before leaving the room.
Most participle adjectives ending in –ed don´t have an adverb form , so we can use a similar prepositional phrase:
The children walked out of the class in a subdued manner.
She walked into her bosses’ office in an agitated way/manner.