Ethercat installation from repositories - how to step by step

Try


For me is says it can find libtool at 
 *** 2.5.4-4 500
        500 deb.debian.org/debian trixie/main amd64 Packages

But I'm on trixie so not identical.
 

Did you do
sudo apt update
before
sudo apt install build-essential
?

hängt ab von means depends on
keine means none

unfortunatly i did do the sudo apt update already that would be to easy
just tried again and tried the build essentials afterwards it tells me it is already the newest version 12.9


should I do a reinstall with the english language? It seems od to me that this would depend on the language.

Is /etc/apt/sources.list broken?

how do i test this? (and fix if broken)

Show the content here it's not many lines.