Module in Backend are working very slow

I am useing Joomla 2.5 and have created many menus. As more menus I have created (with about 135 submenus within each one) as slower were the modules in Backend working or reacting. After I have created about 100 menus it takes about 22 minutes till a opened module is reacting in backend when I push the "Save" Button or "Copy".

What can I do? I need many different Menus and its Modules.

Well better ask on joomla forum , we are not experienced in testing joomla limits.

Obviously the problem is because of the template, the plugins or the modules in it, because other user have also Joomla 2.5 and use more than 500 menus without any problem or delay - I have asked allready.

No, speed of Joomla backed doesn't have any connection with template.
If you Joomla with 500 menus is slower than other's Joomla with 500 menus, then your server (hosting) is slower then the other host.

I am useing one of the best and fastesd server in Germany. This could be not the problem.
May be a useless plugin causes the problem. But I don't know what plugins I can disable without bad consequences.

Sorry, but front-end template definitely doesn't have any relation to the speed of Joomla's backend. This is logically, isn't it? Try to uninstall our template temporarily to check this.