There are various ways.
Some nouns add a Y ending to form an adjective (e.g. snow->snowy, squeak-> squeaky, ease->easy).
Some nouns can use suffixes, such as like (hairlike, ghostlike), full (thoughtful, beautiful) or less(careless, lifeless).
Some nouns can be used as adjectives (attributive nouns form compound nouns).
Ex.
I was riding a mountain bike (compound noun). The word mountain is a noun. However, in this case, it is being used like an adjective to tell what kind of bike it is. Some dictionaries classify these as adjectives, others as noun adjuncts (attributive nouns), because the word mountain is not a characteristic of the bike, but is used to mean a "designed-for-mountain-use" bike.
Lovely is describing a noun, therefore it is an adjective.
Nervous is an adjective. The adverb form is nervously.
Comprehensible is an adjective. The adverb is comprehensibly.
Silently is an adverb. The adjective is silent.
Lively can be used as an adjective and an adverb. Adjective: a lively discussion Adverb: step lively
Lovely is an adjective. There is an adverb (lovelily) but it is hard to imagine doing something "in a lovely manner."
Lovely is describing a noun, therefore it is an adjective.
creating
Use the suffix -ly when you want to change an adjective to an adverb. Ex: The girl is beautiful; adjective The girl spun around beautifully; adverb
Leisure is already in its adjective form. It does not change between noun and adjective, only between noun/adjective and adverb. "Please complete this at your leisure." = noun "My favorite leisure activity is golf." = adjective "He completed the task leisurely." = adverb
Dark can be an adjective or a noun. Darkly is an adverb.
No, -ful can be added to a noun to form another noun or an adjective. Examples: spoon (noun) spoonful (noun) hope (noun) hopeful (adjective) Usually, the suffix -ly is added to an adjective to create an adverb. Examples: usual (adjective) usually (adverb) hopeful (adjective) hopefully (adverb)
Lovely is an adjective.
Just take the "ly" off. The word near can be an adjective, adverb, or preposition. When it modifies a noun, it is an adjective. Adverb: There was nearly a disaster. Adjective: The outage caused a near disaster. Adverb: He came near. He is nearly here. Adjective: There was a house in the near distance.
Completely is already an adverb. Removing the -ly puts it in adjective form.
Night: noun an: adverb adjective: adjective noun: noun adverb: adverb
Guilty is an adjective. If you were to change it to guiltily, describing how something was done, then it would be an adverb.