Hello,
Very strange because we don’t have such issue during import on our test installs. Anyway, you can import this page manually using xml file. All the XML files you can find here https://www.8theme.com/download-plugins/
Download archive, extract, find about-gym folder and find dummy.xml there. Go to Tools > Import > WordPress > upload xml file and press import. Go to Pages and there you’ll find About Us Gym page.
Regards