Loader Layout between levels

Hi.

I have made a loader layout and for the game starter.now how can I make a loading before levels in game ?

and is it necessary (the game has a lot of physics) ...?

I ask this because I noticed after the first loading, going to to levels layouts takes no time and it's immediately.(I just tested it with PC)

the game is for android and ios

tnx for any guide

Yeah it's not necessary, just make sure whatever you are going to use in the current layout is there at the start.