Hello Group,
i want to disable the left navigation, how easy can this be handled?
many thanks in advance.

silentone

You mean remove the left sidebar? Just deselect all page options under "LEFT sidebar: Display on:" and clear all its design elements in the Sidebar Option page.

Sorry for my dumb question, where can i find this option?

At Site Admin -> Appearance -> Atahualpa Theme Options -> Sidebars