Hey,
Because you have set two menus: one with login sign up and another is with language switcher. either you can change menu to topbar or
Please goto
wp-admin > appearance > customize > custom css > paste & save.
@media(max-width: 991px){#menu-topfotstudent{
display:block !important;
position:absolute;
left: 0;
}
#menu-topfotstudent .menu-item-object-page:nth-child(1), #menu-topfotstudent .menu-item-object-page:nth-child(2), #menu-topfotstudent .menu-item-object-page:nth-child(3){
display:none;
}
}
refer:
http://prntscr.com/mbeevu