I like your artwork, & I think you should leave the Polish text untranslated. The gameplay & affordances should speak for themselves plus it's more exotic without localization, like some baffling Czech animation you catch on tv late at night.
For contrast in the world switching, there needs to be a substantial mechanical difference. My suggestion would be that the gloomy world is the depressive-realist view of your downtrodden protagonist, & the other world is her escapist fantasy where she's a wall-jumping parkour ninja: 1984 meets Mirror's Edge (which I suppose would be a bit like Brazil, Terry Gilliam's take on Orwell's nightmare).
In any case, my main suggestion is make it faster & jumpier ![]()