I hope you are well today and thanks for posting here.
I could confirm the issue on my test site therefore notified the issue the theme developer so that it will be fixed in the future version of theme.
In the meanwhile you can fixing it by adding the following CSS code in the Custom CSS option of your theme on the below path.
Admin Area -> Appearance -> Customize -> Shapely Options -> Other
@media (max-width: 991px){
.menu ul.dropdown-menu li a {
width: 90%;
}
.main-navigation ul ul li:hover > ul, .main-navigation ul ul li.focus > ul{
left: 0;
position: relative;
}
}