Sorry if this is reposted but it seems like the website didn't post it before. How could I set up a system to kill players when they touch specific meshes and send them to a checpoint?

I'm a beginner in unity (like I have 4 hours of experience) and a little bit less of a beginner in c++ (probably spent about...6-7 hours coding total). I'm building a prototype for a 2d platformer, somehow I've made good controls and made the camera follow the player, but there is no death system yet which...isn't very good because when the player falls down a pit they just keep falling forever and when they hit a spike, it just acts like a normal platform at the moment, I was wondering how to make a death system (and possibly a checkpoint system) for when they hit a spike or hit an invisible mesh that Is under a pit that will "kill" them and send them back to a specific point.