Hey Panagiotis,
I am really sorry for the delay of this reply as it is a weekend for us here.
I have tried to upload the Easyblog launcher installer zip file through in your Joomla backend installer, it seems like I hitting this error :
Error
There was an error uploading this file to the server.
Unable to find install package
So I've checked your current php information, it seems like your upload_max_filesize is already set to 150M, by right it should not hit this above error because the upload size already set very high.
Then I try to use second installation method install from directory, try to connect with your FTP server and create a new directory folder but I hitting this
Disk quota exceeded warning.
Response: 550 Can't create directory: Disk quota exceeded
Command: MKD /public_html/joomla/tmp/eb5
Response: 550 Can't create directory: Disk quota exceeded
I think you have to consult with your Webhosting provider regarding this, it seems like your hosting limited webspace or your server disk space already full.
Keep us updated once your hosting response you.