Style dropdown, add padding to submenu list items

I am having problem with addressing the submenu (dropdown). I would like to add padding to the list items in the submenu but can’t seem to find the right tag. How can I do this?

And another question – in my attepts to remove the arrow pointing upwards in the submenu the only thing that worked out was:

.navigation-classic .primary-navigation ul ul:before {
content: none;
}

Will this be causing problems? Is there a better way?

Thank you!