how can I make the character bounce off the edge

how can I make the character bounce off the edge??

Not sure I understand the question… Could you explain in more detail?

character goes over the edge how to fix

are you making a platformer game and the character is falling through the platform? Take a look at the platformer game example. You need to use “platform” behavior on the objects that you want character to stand on. And make your character a “platformer character”… Check the “behaviors” are right.
https://editor.gdevelop-app.com/?project=example://platformer