I am new to that stuff and asked Gemini for help. But a few steps further there the problem came: Gemini said to install dotnet from https://dotnet.microsoft.com/download/dotnet/8.0 and then opened a new Folder for the App and Gemini said to open that folder in VS Code and write in the Terminal that Code: dotnet new wpf -n AppNameOfFolder
That command didn't work, it should make WPF-Projekt and the folder should contain these: MainWindow.xaml, AppNameOfFolder.csproj
.NET 8.0 downloads for Linux, macOS, and Windows. .NET is a free, cross-platform, open-source developer platform for building many different types of applications.