ThanksRoy theme - how to slow down main navigation submenu?

Using the ThanksRoy theme, there is an ugly thing for me when I put mouse over a menu item that contains submenu positions. The sub-menu displays suddenly and all the main navigation positions below are moved down together with the search box and footer.
This is very annoying especially when I move mouse quickly up and down over the navigation menu.
Is it possible somehow to delay or slow down opening the sub-menu on mouse over?