You need to:
- Increase memory_limit
- Increas php_max_execution time
Edit your .htaccess file and add the following:
php_value upload_max_filesize 1000M php_value post_max_size 2000M php_value memory_limit 512M php_value max_execution_time 180 php_value max_input_time 180
If you have access to your PHP.ini you can also do it directly in the php.ini file.
Read more here: https://premium.wpmudev.org/blog/increase-memory-limit/