you need to set your Character/Pawn in the GameMode as Default Pawn.
You can edit thr default GameMode in the Project Preferences under Maps & Modes.
Or you create your own GameModeBase class and set this as GameMode in the same Project Prefs, by overwriting the default one.
Second Way is recommendet!
About your question for physic and dropping the char to floor.
In your Character Blueprint, open the class defaults on the right and search for simulate physics (you can seatch with the searchfield at the top). Tick it so true and the character now has physics…
Better:
In the Construct script, add a Line trace going from thw character location to Character location - (0,0,1000) and set actor location on the traces Hit Point.
And for any other of those Questions…
I really really REALLY(!!!) recommend you just type in “Unreal Beginner Tutorial” in the Youtube Searchfield… and no matter what Video you look… nearly all of them can help you…
You can find most of your answers instantly, with Video support, on YT…