Backup your php.ini file before you do anything.
Then open the php.ini file so that you can edit it.
Check that file_uploads is set to On (needed to upload files via a PHP script).
Set upload_max_filesize to 64M (or less).
Set post_max_size to 64M (or less).
Set memory_limit, to 64M (or less).
Set max_input_time to 600 or less.
Set max_execution_time to 300 or less.
Save your php.ini file.
(or minimal modifications):
upload_max_filesize = 500M
post_max_size = 500M
max_execution_time = 500