If the question is just “How to start over?” — Then, you’d just use phpMyAdmin on your server, delete everything in your database, and then re-install WordPress. You could probably do an export of all your posts and pages before that so you could import them after re-installing WordPress.
I set it up in the builder to have 4 columns and 3 rows but no matter what settings I put in the builder, it always comes 2 column.
I’m not quite sure how that is possible unless something is preventing your layout from saving. You’d be able to tell by saving your custom layout and then refreshing the entire admin page and seeing if the options are set properly or not. If not, I would double-check that you’re actually editing the correct layout and that you have your settings setup correctly to be showing the layout you’re editing on whatever page. I can’t see what specifically you’ve setup to tell you what that would be because when I try to view your site, you’ve got it password protected.