500 Internal Sever Error

I notice several things about my Centos 7 server:

I am not able to log in to one of my user accounts despite having the correct username and I changed the password. I got a red failure error.

The WordPress website for greatiamministries.org is slow to load, the administrative panel is low to slow to load, and I sometimes lose the database connection.

I get 500 internal server errors from WordPress.