Hi! Thanks to Paul1031 and to Aman204!
I made a backup, and after I installed JAEM, but JAEM did not find any T3-Framework, so I downloaded the T3-Framework of 29 Sep 2017 v.2.7.0 from your website, and installed it as a normal Joomla extension. The installation seems successful. I have not lost the previous template settings!
However the images still do not appear. So I tried to check all the site and server caches, but I could not find any cache enabled. Do you want to check my server?
I tried to load the homepage both on Firefox and on Chrome, but the result is always the same.
After manually installing the T3-Framework, JAEM found it. So maybe, first T3-Framework was not present at all!
Maybe I did not understand your suggestions. Here it is 11.58 PM, so, next time I will answer you in at least 7-8 hours.
Thanks!
Cheers