If you are using Bootstrap 3.0+, u can follow this:
https://github.com/wp-bootstrap/wp-bootstrap-navwalker
Another reference link you can follow is this one:
https://code.tutsplus.com/tutorials/how-to-integrate-a-bootstrap-navbar-into-a-wordpress-theme–wp-33410
Usually, when you have an HTML menu (not talking about Bootstrap specific), its better to just generate the regular WordPress menu, than apply the styles you have on the original menu.