How can you change the adjective lovely to an adverb?

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.