Do I have to learn another language (CQL) to work with Cortex?

No, you can take advantage of all of Cortex's features without learning CQL. The Query Builder's CQL Explorer includes a dropdown interface, so you can easily construct insightful queries. This extends to Scorecards, allowing you to write custom rules without learning the language. 

CQL is likely the best path for power users — if you're comfortable with JQ or OPA, you can leverage those, and you'll likely find CQL is a low lift from there.