The english page is here but it is far behind the French page in content. We need more English speakers contributing to this amazing project.
In my experience, the .pem extension is irrelevant. I generate a .crt file for the public certificate and a .key file for the private key counterpart, and I simply reference these files appropriately in the configuration files. Sometimes people instead use crt.pem and key.pem for these files, but either should work as long as the content of those files is correct. Your intermediate_CA.crt file can be appended to the cert.crt file to simplify things.