To all who are struggling with this, I solved it in the following way:
nano /etc/my.cnf.d/mariadb-server.cnf
//then comment the following lines:
[mysqld]
#datadir=/var/lib/mysql
#socket=/var/lib/mysql/mysql.sock
log-error=/var/log/mariadb/mariadb.log
#pid-file=/run/mariadb/mariadb.pid
nano /usr/lib/systemd/system/mariadb.service
On the following line remove $MYSQLD_OPTS $_WSREP_NEW_CLUSTER
ExecStart=/usr/sbin/mariadbd $MYSQLD_OPTS $_WSREP_NEW_CLUSTER
To,
ExecStart=/usr/sbin/mariadbd
Leave the rest as same