Dualboot Pop_OS and Window with Burg launcher

Hi

I want to dualboot Windows and Pop_OS

From my understanding I can do everything that Ubuntu can do with Pop_OS, so I should be able to install BURG. This seems not to work.

Where I am:

I am running Windows since some time and I am planing to switch over to Linux. My notebook is already running Pop_OS. With my desktop I am planing to do this step by step as I would like to keep my games and windows only programs on my Windows partitions. (I finally have everything set up as it should be…For my Linux system I bought an additional 500GB SSD. So I installed Pop_OS on this SSD. It works perfectly if I switch the bootdrive in the bootmenu or the Bios. But that i don’t have to press F2 like a mad man every time I boot up my PC i would like to boot into the bootloader BURG
Strangely the GRUP bootloader was not installed. I left almost everything on default in the Pop_OS installation settings. Just chose my additional SSD as location. (and changed time and keyboard layout)

Then I did everything like described in this YT video https://www.youtube.com/watch?v=qu2e9LBBS6g

When I do the first step it already gives me errors saying that the reposetory can not be installed due to a missing release file.

Im Swiss so the errors are in german sry:

Das Depot »http://ppa.launchpad.net/n-muench/burg/ubuntu eoan Release« enthält keine Release-Datei. N: Eine Aktualisierung von solch einem Depot kann nicht auf eine sichere Art durchgeführt werden, daher ist es standardmäßig deaktiviert. N: Weitere Details zur Erzeugung von Paketdepots sowie zu deren Benutzerkonfiguration finden Sie in der Handbuchseite apt-secure(8).

How can I get this to work?

Janick