Hi there,
you can try some CSS like this:
.dropdown-hover .main-navigation:not(.toggled) ul ul li:hover>ul {
max-height: 500px; /* Adjust this height to suit */
overflow-y: scroll;
}
This will apply to any of the sub – sub menus by limiting the height which you can adjust to suit.
If you want to apply it solely to the afrika sub menu then you need to add a class to that parent menu:
https://docs.generatepress.com/article/using-the-wordpress-menu-builder/#custom-classes
e.g class name of: scroll-menu
Then your CSS would look like this:
.dropdown-hover .main-navigation:not(.toggled) ul ul li.scroll-menu:hover>ul {
max-height: 500px; /* Adjust this height to suit */
overflow-y: scroll;
}