Hi. Try this code
.sp-megamenu-parent .sp-dropdown .sp-dropdown-inner {
overflow: visible;
}
But keep in mind that the Joomshaper team set it overflow: hidden; from the box for design reasons. If you apply this code, then the lines will climb outside.

And you will need additional CSS coding to get rid of this.
The design of this template is not designed for the 3rd level of the menu. This is not a bug, but an erroneous design feature. I would do it differently so as not to affect the 3rd level of the menu. But what is, that is.
Use commercial templates as it is. Or pump your CSS skills if you want to change it.
The best template for developing any design is pure Helix Ultimate