Server Requirements are very critical in order to seamlessly upload the theme and import the demo data. Below is the list of configuration parameters of php.ini file that should be verified before installing the theme.

max_execution_time = 300 (900 if you are using GoDaddy) 
max_input_time = 120
memory_limit = 128M
post_max_size = 15M
upload_max_filesize = 8M
PHP Version Minimum 5.4 But batter is if you can go with PHP version 7.0.0 Minimum

How can this be checked?

1. You can check this in the php.ini file on your server and modify them as necessary. If you are not familiar with modifying this, you can reach out to your server hosting provider who should be able to configure this for you.
2. You can install and activate a plugin called WP System Information. On activating the plugin, the PHP Info can be found by navigating to Tools > System Info. You can then reach out to your server hosting provider who should be able to configure/modify this if required.
3. Also, you can check your site health from WordPress Dashboard then Tools > Site Health
   where all of the necessary information is available.