Mysql issue

I have changed some values in my.cnf file under /etc/mysql/conf.d and restared mysql service.
It's now not starting i am getting following results from service mysql status

May 11 17:38:16 s1.xxx.xxx mysqld[24127]: 180511 17:38:16 [Note] InnoDB: Waiting for purge to start
May 11 17:38:16 s1.xxx.xxx mysqld[24127]: 180511 17:38:16 [Note] InnoDB: Percona XtraDB (http://www.percona.com) 5.6.36-83.0 started; log sequence number 1600617
May 11 17:38:16 s1.xxx.xxxmysqld[24127]: 180511 17:38:16 [Note] Plugin 'FEEDBACK' is disabled.
May 11 17:38:16 s1.xxx.xxxmysqld[24127]: 180511 17:38:16 [Note] Server socket created on IP: '127.0.0.1'.
May 11 17:38:16 s1.xxx.xxxmysqld[24127]: 180511 17:38:16 [Warning] InnoDB: Cannot open table mysql/gtid_slave_pos from the internal data dictionary of InnoDB though the .frm file for the table exists. See http://dev.mysql.com/doc/re
May 11 17:38:16 s1.xxx.xxx mysqld[24127]: 180511 17:38:16 [Warning] Failed to load slave replication state from table mysql.gtid_slave_pos: 1932: Table 'mysql.gtid_slave_pos' doesn't exist in engine
May 11 17:38:16 s1.xxx.xxxmysqld[24127]: 180511 17:38:16 [Note] /usr/sbin/mysqld: ready for connections.
May 11 17:38:16 s1.xxx.xxxmysqld[24127]: Version: '10.0.34-MariaDB-0ubuntu0.16.04.1' socket: '/var/run/mysqld/mysqld.sock' port: 3306 Ubuntu 16.04​

Now i haver restored original my.cnf file but still i am gettings same errors how can i fix it?

 

restore your backup of mysql database aswell

 

I can't backup my databases with
mysqldump --all-databases > dump-$( date '+%Y-%m-%d_%H-%M-%S' ).sql -u root -p


mysqldump: Got error: 2002: "Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2 "No such file or directory")" when trying to connect

When i start mysql;

mysqldump: Got error: 1932: "Table 'xxx.xxxx' doesn't exist in engine" when using LOCK TABLES

 

you were supposed to backup data before you make changes. this is why.

 

There no way to fix this issue?

 

depends, what did you change and hopefully

did not do any bad

https://www.softaculous.com/board/index.php?tid=4098&tpg=all&title=MySQL_not_starting_up

 

I was just changing some values in my.cnf file for server optimization.
Now i restored original file but still same issue..

 

yeah, you screwed up your innodb-tables. if you don't have any other innodb-tables besides those in mysql database, you can try reinstalling mysql database after deleting your innodb-files in mysql-data directory.

 

I have just one website database and system databases

 

Can someone help me please?
My server is down now

 

So you have no backups from before you changed datebase settings? If that is the case, I would pay someone who knows databases to attempt fixing the db.