How do you change the word completely to an adverb?

You can change "completely" to an adverb by adding -ly to the end, making it completely.

It's already an adverb!

However, if you want to express a similar meaning with a different word, some alternatives include:

* Totally

* Entirely

* Absolutely

* Thoroughly

* Utterly

* Full (as in "full of joy")

* Wholeheartedly

The best choice depends on the specific context and the nuance you want to convey.