So I want to create a map where people can respawn from very high above, but there's a black square, sort of like boundaries, reaally low so I cannot create spawn point high above because it gives me an error. What can I do?

And I have 2nd problem, so I like built a map and a floor, but when I started playing it wasn't a floor, just some ttexture and we kept falling down, HOW DO I FIX THIS???? It's about soldat map editor

Try adding some polygons upon the spawn,
as for the falling through - use the compile function.

Soldat Polyworks is the best option for compiling a map :)

for your second question you probably didnt compile it.