As it is seen from your error log Revolution Slider plugin is already exists on your web-site. So probably you just need to activate it in Plugins section. Or you can remove wp-content/plugins/revslider and install it again.
Search function can be disabled in Theme Settings – Header.
We just opened your server files and see that revlsider folder was here. We are not able to delete it through the FTP (we don’t know why but the process is too slow). So we just renamed it so you can install a new copy of the plugin. But we suggest you to remove the folder with SSH or via cPanel