Underline pointer length is too long & distance from menu is excessive

Hello. I have been developing my website for weeks now, and I have encountered 2 problems regarding the navigation menu underline pointer. 1) How can I shorten the length of the underline pointer such that it only underlines the word on the navigation menu? 2) How can I reduce the distance between the navigation menu word and the underline? For now, the underline is too distant from the navigation menu word.