[TYPO3-install] Typo3 crash after extension installlation

[Luigi Negretti Lanner]

Hi all, I hope this is the right forum, anyway:
 
I'm starting now to use Typo3, and I'm trying to test typo3 7.6 4 on my local server. My OS is CentOs 6.5. I've installed typo3 without particular problems (after setting up some php configurations as required by typo3 installation), but when I try to install some extensions (for example extbase), through thie extension manager present on the backend,  what it occurs is that after I make click on the download icon and that I can see the upload bar for a few seconds nothing else happens (no message of error or of installation successful), and when I reload the page, the website (both the frontend and the backend) is simply disappeared, I can see only a blank page, without any chance to access frontend or backend. What can be the issue? I have a not too much efficient internet connection, could be some issue related to the download process?