The article is 10 years old, I presume/hope things changed. Any source about current situation?

As this is not mentioned, is it possible to extend the system by collecting rainwater falling on solar panels ?

I am Collins (20th century boys)

Talking about apps I would recommend MosaLingua (digiSchool), it helps me for English and Spanish.

It’s mainly design to learn vocabulary (spaced repetition), the app is free, only class/courses may required a subscription.

Answering your initial question you can select the “native” language you want, but I’m afraid you won’t find your mother tongue.