It seems that you have a problem with the server settings, this is a timeout errors, could you please try to change the settings to the one you can find in this article : What To Do If Demo Content Import Fails
Also try to contact your host support, they should be able to tell you exactly what they can change to fix this.
Do not hesitate to contact us if you have more questions.
I upgraded my site to the latest version yesterday and since it has run ultra slowly. There was also an error appearing in the log file.
/index.php
[error] ap_content_length_filter: apr_bucket_read() failed
Hello David,
It seems that you have a problem with the server settings, this is a timeout errors, could you please try to change the settings to the one you can find in this article : What To Do If Demo Content Import Fails
Also try to contact your host support, they should be able to tell you exactly what they can change to fix this.
Do not hesitate to contact us if you have more questions.
Regards.
---------------------
Hosting we recommend ( Free SSL and CDN included in all plan ).
Speed up your site with Autoptimize
Test your site with GTmetrix and fix the issue to make it faster
How to Update your Theme