Add below code
#site-navigation .menu > ul > li.menu-item-has-children > a::after {
content: '\f107';
font-family: FontAwesome;
font-size: 10px;
margin-left: 10px;
vertical-align: 1px;
}
#site-navigation .menu > ul > li > ul > li.menu-item-has-children > a::after {
color: rgb(34, 34, 34);
content: '\f105';
font-family: FontAwesome;
font-size: 10px;
vertical-align: 1px;
float: right;
}
Add 3rd level navigation.
If you face any issues, reply.