Hey Aphamino. Looking in the App Store, it seems the iOS version of Machinarium was updated on October 6, 2016, with the ability to switch between several different languages. My iPad can't run that version, so I can't check and say for certain, but I believe you can switch languages from the black title screen with the white Machinarium letters—the one that displays when the game is first launched. (So if you have the game running, you'll need to quit it and relaunch it in order to see that screen.)
Edit: Eh, I used my wife's iPhone version and took a screenshot. (I assume the iPad version is identical.) So you'll want to keep tapping here:
...until you finally see this: