Header Customization (color, height, text, opacity adjustment)

Hello,

Just bought this template am I’m looking forward to using it. I would like to make a few modifications.

1) I would like to reduce the height of the header.

2) I would like to remove the opacity / fading option of the header and just have as a white header, which would remain the same size as you scroll up and down the page.

2a) Since the opacity option would be removed, I would like the home page slider image to start below the header menu.

3) I would like to change the font to a more visible font which would be a bold black font on the white header background and potentially adjust both the spacing of the menu items and the color (A:link, A:visited, A:active, A:hover).

Basically I would like the header to be as it is in this website: https://glacieradventure.is/

Here is my current website (with basically no edits as of yet): https://icepicjourneys.is/