For suggestions/feedback concerning the android app you better post them directly in this topic:
You can create your own custom offer and ask for slow time settings. Then the question will be to find players interested in slower time settings too (there are)
OGS works well in a browser on a mobile phone, that gives more options as an alternative. Both are interesting whatever.
Ranked/unranked: It’s a choice you make when you create/ask for. When your game comes from the list of game offers, It’s clearly indicated too.
(That’s in the browser. I dunno how it works on app.)
Later, when the game is running, the info is under “info on the game”
Perhaps to be clearer: the Android app is just fan-made.
It’s great, but it’s not an official part of OGS and is not maintainted by the OGS team, which is why @Groin suggested this feedback would be better posted in the app thread he linked if it only relates to the app.