I have installed SharePoint Server 2013 with mysql server 2013 on a windows server 2012 on a dell server with Intel Xeon Processor on about 2Ghz and 4 GB ram,(the server is about 7-8 years old) the problem is that the sharepoint website is running extrelly lagged and slow. What you will suggest as an optimal hardware for thoose software products to be running smoothly inside a intranet?
Microsoft posts server limit on its TechNet site. A Single server running SharePoint 2013 with all services and SQL server should have at least 24GB RAM and 8 CPU cores. That's just for basic functionality. If you want to deploy MySQL as well you need to plan for that workload. You won't get a satisfactory experience with your setup.
See the official requirements here: http://technet.microsoft.com/en-us/library/cc262485.aspx
As Jesus said, 4 GB RAM is not enough. Search alone eats 8 GB RAM.