So I need to implement an map-like UI and a Stats panel that is right on top of the map. I tried using @showUI UI1,UI2 but the second UI is always disappearing the next second. I tried with Play-Script and with normal scripts but it's always the same problem.

It is likely because the UI's Sort Order is below the other UI's Sort Order. You can adjust the Sort Order in the Canvas component in the UI prefab.