Several Style/Thematic Questions For Highend Church Theme

Hello all,

I’ve recently started making some changes to my website to give it a bit of a facelift. I am using the Highend Church theme. I really like this theme and have started to draw some inspiration from its style.
Now, I have a number of questions on how to achieve the look I want. Forgive me if some of the questions I ask are a bit underwhelming(or overwhelming), I am fairly new to webdesign the WordPress way.

1. Notice the “Donate” link on the navigation bar of the demo website. It seems to be have a bold face is underlined. The color of the text is also persistently in the accent color as well. When moused-over it turns black, which happens to be the opposite of the effects on the other navigation links. How would I do this with a single navigation link of my own?

2. There is a dropdown megamenu for the “About” link on the navigation bar of the demo site. This megamenu has a one column dropdown menu. For some reason my dropdown cannot go any lower than two column. My megamenu is setup like this
[Parent -> Child1 (two children) | Child2 (no children)]
That is to say that the menu has two child links, and one of said child links has two more child links of its own, the other does not. What I am experiencing now is a situation where the ‘Child1’ and ‘Child2’ links are in different columns and when moused-over do not behave as a link, despite being one. However, the 2 child links of ‘Child1’ do behave as links (the cursor indicates the text is a link upon mouse-over). Ultimately, the look I want to achieve is similar to the ‘Portfolio’ megamenu on this demo site: https://hb-themes.com/themes/highend_wp/. If it is possible, how can I do this?

3. When I try to display a map, using the Highend map settings, I get an error when the map loads. Is it because I need an API key? That’s the only information I haven’t typed in on the map settings page.

4. I have a sticky header with my logo in it. Is there any way to make the logo get smaller with the sticky header when scrolling down, or am I going to have to make the sticky header size large enough to accommodate my logo?

5. Is there any way to make the sticky header opaque?

6. Is it possible to make the top header bar show on mobile?

7. Is there any way to change the forward slash navigation menu separators to something else?

I know that I have asked quite alot, so I am not expecting a quick reply. As stated earlier, I am pretty new to WordPress, but I have a desire to learn all I need to get my site looking presentable. Thank you for any help offered.

Highend Church demo site for reference:
https://hb-themes.com/themes/highend/church/