Need help - Passing through mesh, why ?

Hello, as said in the title, I need help ( I’m a newbie).
Short story, I was assembling some mesh together in a 3rd person world, I press play and when my character run onto some mesh he pass through them.
Why ? How to make it so he does not pass through them anymore ?

I would gladly like to provide more information if needed.

Hey! Your character is most likely passing through the meshes because they don’t have collision enabled. This should help you get your problem fixed: