Use APKPure App
Get Mongolian Keyboard old version APK for Android
Wir können Text in unserer Muttersprache zu schreiben.
it has layout like pc keyboard locations. so when write something on your phone you can use your tow hand.
Settings->Language & keyboard -> Mongolian keyboard -- check it.
after that when you write something, long press on text input and choose Input method -> Mongolian keyboard