'thoroughly' adverb would be used as an intensifier to modify a verb, adjective, or other adverb. It indicates the degree to which an action is carried out and is used to emphasize its thoroughness or completeness. For example, when someone says that they 'thoroughly cleaned' the room, it means that they put great effort into doing a thorough job.
1. I thoroughly enjoyed the movie.
2. The students thoroughly prepared for their presentation.
3. She thoroughly reviewed the documents before signing.
keep in mind that while 'thoroughly' is an effective way to emphasize the quality of an action, overusing it can make your writing seem clumsy and repetitive. It is therefore best to use this adverb sparingly.