First, I decompiled the DLL file using DotPeak. Opened the .cproj file in Visual Studio. After searching for a solution to the problem on the Internet, I installed libraries 4.0 ( Microsoft.NETFramework. ReferenceAssemblies.net40 ) from the NuGet website into the frameworks folder. And this window as in the first screenshot disappeared. But after I compile the project, many errors appear like cs1525, cs 1002, etc.
So, how can I work with an old project in the current version of Visual Studio?