Responsive menu overlaps content

I’ve built a child theme of Simone. It functions both as a one-page website and a blog and has two menus – one for the one-page website and one for the blog.

I have a problem with the mobile menu for the the one-page website. When you click an item from the menu, it takes you to the appropriate section of the front page but doesn’t collapse afterwards. This way it overlaps the content and makes it unreadable. I don’t know what causes it. I’ve lost a whole day trying to solve this problem but I haven’t succeeded.

The website in question is: https://myowndesigns.info/
The screenshot of the issue is: https://www.dropbox.com/s/7q4r74alvmvnx1v/mobile%20menu.png?dl=0