You can choose the language you want to play in from the Settings menu. To access it, select the cogwheel icon at the top right of the main screen.
When you enter, you will find the language option under the Sound and Music icons. If you press on it, you will see a drop-down menu where you can choose your preferred language.
Keep in mind that changing this option will change both the language of the game interface and the language of the questions.
We invite you to read the article: Why do I see questions specific to other countries? and What can I find in "Settings"?