Problem updating plugins and WordPress to new version

Hi,

I am having trouble updating my site which uses wordPress theme twenty twelve as a template. I recently installed a child page so I could make the site responsive.

I want to update WordPress to a new version and also all of the plugins that need to be updated but I receive this error all the time:
ERR_EMPTY_RESPONSE: The server closed the connection without sending any data

I tried deactivating all the plugins to update WordPress but there is no use…