This error message usually means there is an execution time limitation on your server. We recommend you to contact your server provider to increase the execution time.
You can also take a look at this tutorial if you want to try it yourself.
But note this is not enough, you must set the ‘Front Page Displays’ to ‘Home’ than latest blog posts via Settings->Reading. Also, please select Navigation Menu via Appearance->Menus->Manage Locations.