1 or 2 columns

I mean that it is not going back to 2 columns when I click on 2.

I mean that it is not going back to 2 columns when I click on 2.

While in “screen options” in the Admin Area?

that is right

try placing this near the bottom of the wp-config.php just before the require_once line:

define('CONCATENATE_SCRIPTS', false);

Documentation

what is the wp-config.php? Is that in admin?

That is your configuration file.

To start with, look in WP root (NOT in wp-admin, wp-includes or wp-content).

I would backup the old wp-config.php file.

It’s possible you’re looking at a cached page. Just in case, you might want to check on a different browser (or clear your cache).