1. It is J.R.R. Tolkien who imagined and built the Elvish languages, that's why they are called "constructed" languages and not natural languages.

2. Even if people often speak of Elvish (singular) these languages are many (! over 10) and very different from each other. They are all part of one family, like the Latin languages are all descended from Latin (French, Spanish, and Italian).

3. The Elvish languages are as complex as the above natural languages. They are not regular. The Elvish languages are complicated.

4. No one speaks fluently Tolkien’s Elvish languages.

5. People do not speak these languages not because Tolkien did not finish them (as often misguided people write) but because the grammar rules and words imagined by Tolkien have not (all) been published. We miss some of the explanations of the rules.

6. Tolkien also imagined/invented Elvish writing systems: the Tengwar, the Cirth, the Sarati, the Runes of Gondolin, the Valmaric script. These are extremely complex and have rules too just like the Elvish languages.