This is a very basic design element of Elementor. If you are using a theme that allows full width layout, then all you have to do to create a full width section with multiple columns is this:
If you find that this doesn’t work, then your theme may not allow full width layout. Luckily, Elementor has a solution for that situation as well. Follow steps 1, 2, and 4 above, but replace step 3 with this: Click on the Section and from the Layout area, look for “Stretch Section” and switch it to “Yes”.