You can disable data collection in the settings, or directly install Firefox Klar, a special version of Firefox Focus without telemetry made for Germany, Austria and Switzerland.
As others have said, the option to disable telemetry is in the other stores.
Read the article, it says it too:
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You can turn off the anonymous data collecting of Firefox Focus by tapping on the settings icon, and flipping the switch next to "send anonymous usage data" to off.
only 3 country care about privacy?