[Theme: Cluster] How to change the header space

Hello everybody! I have a blog for almost 4 years now, but up to last month I had someone who helped me with the theme changes and stuff (I mainly only produce the material and do minor changes like in widgets). I’m trying to change the header of my blog, which is https://www.temperaria.com.br . As you can see, now I have the main menu and logo up, a huge space and them the captain slider. I want to take this space out, but I’ve been looking into the CSS and other topics here for more than 3 hours and I was not able to find out how to do this. Can someone help me with this matter? I really appreciate your attention and assistance!