Can not upload the .zip file (onepagePro Theme) to Wordpress

This Error was shown, when I upload the Theme to Wordpress-Dashboard
Have someone an idea how I can solve the problem?
Thanks for your help!

Internal Server Error

The server encountered an internal error or misconfiguration and was unable to complete your request.
Please contact the server administrator at [no address given] to inform them of the time this error occurred, and the actions you performed just before this error.
More information about this error may be available in the server error log.
Apache Server at www.mywebsite Port 80

I would like to recommend you please contact your hosting support and tell then to check your server error log and give you solution/support to fix this. If your hosting support tell you it is occuring due to theme issues then you can check this:
Theme Installation Problem:


If you have still problem with the theme then The best way to get the support is Contact your purchased Theme Author. Contact Author because Item Author are best expert about their Item functionality.

Hello!
Thanks for your answer.
Can you tell me how I must install the unzipped files from (onpagepro.zip) on the Wordpress Themes surface. Thank you.
Best regards
Maggie