Is it possible to get the information of which user changed what in a database?
The right direction for this is to use an audit logging plugin. There are some choices out there. Please check out the following post for more information

http://www.mysqlperformanceblog.com/2014/05/20/database-auditing-alternatives-mysql/

My personal preference is the Percona Audit Plugin but you should be using Percona Server (MySQL Alternative) for this.