Excavate a 5m x 5m x 5m pit with a mini excavator

One greatly underestimates in such burial situations how heavy earth actually is. If people can already be buried by significantly lighter snow, they get crushed by earth. It's not about a few crumbs falling down, but rather quickly about one cubic meter falling on someone. And that can quickly be a ton or more. As long as someone is only buried so deep that their chest and so on stick out, they can hardly suffocate. That’s why the slopes only apply from a certain height. YouTube instructional videos are a nice thing for simple matters where you just want to copy something to do it easier and better. For life-threatening matters, one should have more knowledge or be trained by experts.

for the completely buried it was game over

I believe the OP has been sufficiently informed that his project as he plans it cannot work. Please don't be mad at me if I close the thread at this point before any life-threatening DIY instructions appear.