After research I found out, that GitHub has updated their authentication policy, where it is no longer possible to use basic authentication. After research and talking to colleges, who participate in the same courses, I found that GitHub provides a service called Authentication Tokens. With using these authentication tokens, I was able to authenticate with the GitHub server in the Eclipse IDE, where I used the authentication token and inserted it into the password field. With that, I could use the git tools provided in the Eclipse IDE and interact with the remote repository. As the Git support in the Eclipse IDE, I searched for another solution. There I found that GitHub provides a Windows application called GitHub desktop, which automatically connects to GitHub when provided with the correct credentials. With that, I was able to fully interact with the remote repository, but I still had no command line options to execute git commands on. At last, I found the solution to my problem. The problem was, that the git client does not automatically check for updates. Therefore, I had an old git client, which was not able to communicate using the updated GitHub authentication. To finally fix this problem and being able to communicate with GitHub again, I needed to execute the command git update-git-for-windows. With that command, I was able to update my Git client and was now able to authenticate with the GitHub server using the new OAuth authentication method.