Re: Text setting
Currently it is not possible, @Voice app reads the entire text in a file or article with one voice (e.g. English voice or Polish voice). To some extent it would be possible on Android 8 (Oreo) devices when using Google TTS voices. Google recently introduced an experimental feature there to automatically recognize language and use separate voices to read text in a multi-language file. But for this to work reliably the phrases have to be at least 4 or 5 words long - it's a statistical process of guessing the language, for single words may make a lot of mistakes.
Technically it would be possible with some annotations that tell the reading program in what language a range of text is. But at this time I don't have any support in @Voice app for such annotations. I may add this in the future, if more users request such feature.