Can add another sidebar ?

You can do whatever you have the CSS and (x)html skills to do. Your theme files are in wp-content/themes/YourThemeName and there’s nobody stopping you from hacking ’em up.

Or, you can see if there are any 3-column themes you like at a place like https://themes.wordpress.net/ It may be easier to find a theme built for 3 columns and just modify the colors/graphics.

thank u !

i have gotted a theme with four colomn thanks alot HandySolO.