The operating system my web server runs on is (include version): Ubuntu 16.04.4 LTS (GNU/Linux 4.4.0-124-generic x86_64)
I can login to a root shell on my machine (yes or no, or I don’t know): no
I’m using a control panel to manage my site (no, or provide the name and version of the control panel): no
Certificate is working but when try to reach www.domain.com/ it causes an error with security
This website is on wordpress, and I think there is hard redirect to https
I don’t know how to turn off this redirection to even get the website
That's because it's using the certificate for hawk-igpspunchclock.com, which is different. You'd probably be better off putting both names on a single cert, rather than on two separate certs.
If I know it correct (don't use Apache), you have to reload / restart Apache to use these informations.
If it is wrong, then these two files are wrong.
Look in /etc/letsencrypt/live/, there should be another folder with the correct certificate. There is a command like "certbot certificates" to see which certificates exists.