Can you contact your hosting provider about increasing the allocated memory size for your site? I tried to import the demo content manually, but it didn’t allow me to import the demo content. It gives the “504 Gateway Time-out” error message which is related to the hosting company.
They said they have increased the allocated memory size, and I also updated those values like you suggested. But seems it’s still not working when I try to import the demo content. Can you check it, please?