looks like your user naamak is the one casing the high loads.
I would suggest you look into optimizing the site code,
check the database make sure it's indexed properly and does not store " garbage" like orphaned entries / logs
look into implementing a cache system for the site, maybe even consider adding cloudflare cdn into the mix.
In general about your system
Mariadb 10.2 will be EOL in about 4 months.
centos 6 is EOL,
i suggest you upgrade your mariadb.
its also recommended to move forward to a newer distro as soon as possible.