I’ve gone around the problem by creating 3 columns. This makes the mega menu very wide and so the problem doesn’t happen.
It would be good though to know how to make it look nice with only 2 columns.

I created a child theme, imported the parent theme data using that quick easy button in the ‘import / export’ tab.
Then I had to fix my settings for my menu.
And save the Enfold theme quick css.
And my child theme looks normal now.
thanks.