Let me start with I am a complete check_mk and Linux n00b!
I have managed to install check_mk onto a Centos server and I can access the login screen, however when I attempt to log in using the cmkadmin account, the screen just refreshes, no error, no authentication failed, it’s just not loading the webpage after authentication.
As a beginner CentOS is a bad selection. There are all security settings active you can find in a modern Linux. That’s not bad by itself but will not help if you start. I would recommend Debian or Ubuntu for starters and first tests. But this is only my opinion.