Before install the demo you need to increase those limits to a minimum as follows:
max_execution_time=300, max_input_time=600, max_input_vars=5000, memory_limit=256M, post_max_size=48M, upload_max_filesize=48M.
You can verify your PHP configuration limits by installing a simple plugin found here. In addition, you can always contact your host and ask them what the current settings are and have them adjust them if needed