In order to avoid any possible import issues because of your server and php its settings, we would recommend setting up following PHP values in your server’s php.ini:

• Memory Size: memory_limit = 512M
• Script execution time: max_execution_time = 180
• Number of input variables: max_input_vars = 4000
• Php upload limit: upload_max_filesize 16M

You can verify your PHP configuration limits by installing a simple plugin "Host PHP Info":

https://wordpress.org/plugins/host-php-info/

or by creating a phpinfo page. Follow the next steps to create a phpinfo page using your FTP File Manager:

1. Navigate to the directory with you are working. This is important because each folder can actually be set to have different php settings. 
2. Create a plain text file, name it for example phpinfo.php, add following lines and save: 

   <?php  
       phpinfo();
   

3. Visit this page in your browser. If you created this file in the root of your public_html folder, then visit http://example.com/phpinfo.php, replacing example.com with your own domain name.
4. To find the specific value of a setting, search the page for what you're looking for. In this case, simply use browser's search feature CTRL-F (Windows) or COMMAND-F (Mac).

If you don’t have an access to the php configurtation on your server, you can try to set this values in .htaccess file:

php_value max_input_vars 4000 

php_value max_execution_time 180

php_value memory_limit 512M

php_upload_max_filesize 16M

Pls be careful, because some of hosting companies don’t allow to change php settings directly using .htaccess. In case you have some problems after modifying your .htaccess file, log in to your FTP account and remove these modifiactions from .htaccess

In any case you can contact your hoster and ask him to set required settings.