Hi Fadil,

To achieve your requirement you just write CSS code in code injector in the web editor

in the editor section try this:
For border between menus:   

/* Add border between top-level menu items */
.nav-menu > li {
  border-right: 1px solid #ccc;
}

/* Add border between sub-menu items */
.nav-menu li ul li {
  border-bottom: 1px solid #ccc;
}

For '+' or '-' icon:

/* Replace dropdown icon with Font Awesome icons */
.nav-menu .fa-chevron-down:before {
  content: "\f067"; /* Plus icon */
}

.nav-menu .open .fa-chevron-down:before {
  content: "\f068"; /* Minus icon */
}

Hope it helps