Change the way the menu is displayed

Hello, i am using this premium theme http://maidenhair.tomastoman.com/ and this is my site : https://senderosdelchirripo.com , the theme allows me to change the font menu size , but if you see the subitems of the menu, they are like boxed , for example in the GALLERY menu, it looks weird, it seems the submenu box container has a fixed size , is there a way to change it? so that the submenu be read all horizontally?

thanks in advance.