Recommended PHP Limits
Many issues you may run into such as; white screen, demo content fails when importing, empty page content and other similar issues are all related to low PHP configuration limits. The solution is to increase the PHP limits. You can do this on your own, or contact contact your web host and ask them to increase those limits to a minimum as follows:
Also consider upgrading your PHP version to the latest version, the newer the better.
How To Verify Your Current PHP Limits?
You can verify your PHP configuration limits by installing a simple plugin Host PHP Info by Arefly. In addition, you can always contact your host and ask them what the current settings are and have them adjust them if needed. Please note though that many hosts will try to keep the PHP limits low without reason. However you are paying for it, and therefor should be getting your moneys worth.