I'm trying to run an nginx reverse proxy to multiple debian-apache servers inside my network.
I would like to have https via LetsEncrypt through the entire journey (from internet to nginx proxy, then from nginx to the backend server).
Do I have to put the same certificate on both servers? Or can I use certbot to request/renew a certificate on nginx proxy and the backend server?

I'm able to request the regular http page on the internal servers just fine, yet when I try to do https I fall flat on my face.
What would the nginx configuration look like?

I have read so many tutorials and manpages that my head spins.

Thank you!