I’m going to have to look into the SlideShow background further. However, are you saying that you thought the intended behaviour would be that it acts similar to the background photo option?
In regards to your mobile menu, you should be able to toggle the drop-down menus using the down arrow. However, it would appear that the layout default CSS is positioning the menu items to close to the down arrow to toggle the drop-down menu. Instead, it is loading the menu item instead.
To resolve this for the timebeing whilst this gets investigated further you can use the following CSS.
.fl-module-menu .fl-menu li {
text-align: center;
}