I think you are talking about the mobile menu icon. Please add the below code at Appearance -> Customize -> Additional CSS
.toggle-nav {
float: none;
width: auto;
height: auto;
}
.toggle-nav i {
font-size: 23px;
}
.menubar .container {
padding: 0;
}
.menubar {
padding: 0;
}
Correct me if I am getting wrong.
Thanks