Currently, 1Blocker is available in nine languages, and you can easily switch between them in your device settings.
On iOS, go to iOS Settings → Apps → 1Blocker → Preferred Language.
On macOS, the preferred language can be changed in System Settings → General → Language and Region → Applications → 1Blocker.
After that, you will need to restart 1Blocker to make it update the language and change the interface.