Internal Server Error when I try update to 4.2.2 or install Wootique theme

I just started to create a webshop in wordpress and at first I tried to install the Wootique theme downloaded from woocommerce but I recived a message “Unable to create directory wp-content/uploads/2015/05.” Then I downloaded the zip file of the theme manually to the wp-content/theme and after that I was able to see the theme in WordPress and install, but after the installation when I tried to open the front of the website I got this error:
“Internal Server Error
The server encountered an internal error or misconfiguration and was unable to complete your request.
Please contact the server administrator to inform of the time the error occurred and of anything you might have done that may have caused the error.
More information about this error may be available in the server error log.”

I deleted manually in FTP (it was not working the “cancel# buttom in WP) the theme and all plugins installed by me.

Now I can see the default view of the website with the Twenty Fifteen theme “Hello World” but when I try to update from 4.1.4 to 4.2.2 I see the same Internal Server Error that before. Also when I click to the 1 comment that is showed in the front page of my website I get this message:
“Not Found
The requested document was not found on this server.”
even if I can see the comment in the Dashboard of the backend.

These were my first steps in the World of WordPress, there is a chance to fix that?