Highend theme and Child Theme Troubleshooting

I was having a problem with my Hghend theme after first installation, the menu on header where inside the slider. Since I am new to WP and it’s my first time doing a website using a theme, I started customizing my theme on the theme itself and not on child theme. Then I had a notification to update the theme and realized I needed to customize on child theme. I Installed Child theme and then as I am trying to customize it using drop and drag customize (front end editor) I noticed that my home page had a particular section duplicated like 7-10 times per section. I had to manually delete the duplication and then I clicked update to save the changes to bring it back to normal so I can customize with my content, but it does not save. Every time I view my page, it’s the same, the foother is duplicated and I don’t know how to bring it back to normal. So I went on my server and deleted theme and went to reinstall it on WP. Now the original theme I purchased still having the same problem where the header menu is not aligned and is inside the slider and now when I tried to install the child theme it says the theme is missing the style.css stylesheet. Please help, I had spent so much time trying to do this on my own and I’m getting frustrated. Thank you! attached is the screen shot