This is some one related to my isue
I found an oterh topic at this Forum where some one got the same error while installing an other software. .
In this topic the say that the installer is looking for the file in the operating system not the internet. And hence he sould type
deb cdrom
I tried the same and some thing did hapen when I typed the orginal comand sudo app-get install Firefox-esr
To start with a numer of new lines aperas
and att the end I get this mesage:
Releas esr for firefox not found
I starting to wounder if ts the prefix