Is There a similare to registary editor at Linux , and if so how can I use it to modify and add keys , and what is the most important key you modify?

Linux structure is different compared to windows, but we have something similar to windows registry called dconf editor.

If you want to install it via shell:

sudo apt-get install dconf-editor

Or you can use Software Center in Ubuntu to install it graphically. 

In dconf you can disable background images, Manage you apps, proxy settings and so. See its different parts and work with them.