Unable to Configure Certain Things

I need help on a few things please for the Rogan WordPress Theme I purchased. The site in reference is whichoneapp.com. Here are the issues I’m running into:

1. Is there a way, at all, to have the app screenshot that I see on whichoneapp.com show up for the mobile version as well? That’s a big part of the appeal of the site — to be able to see the actual screenshot.

2. There’s a small white line that runs down the right hand side of the website on the desktop version only that I can’t seem to get rid of. Not sure what to do about it. Any idea?

3. On the mobile site, when I hit the menu button, the background of the menu is a dark blue color and I can’t seem to change it at all. I’ve tried under Theme Settings > Menu > Menu Background Color and Background Color but neither seem to be working. I am able to change the link color etc. on both desktop and mobile but not the background color of the menu.

4. Is there anyway to get rid of the menu items on the 404 page?

Overall, I really like the site, but there are a lot of little bugs and issues that have made a bit furstrating, as well as the fact that some things are editable in very unituitive areas. That being said, I’m hoping you can help me on the above to help alleviate some of these issues. I look forward to hearing back and thank you for your time!

Kind Regards