FluentAssertions replace with Shouldly
Just press cmd+H in Visual Studio and replace
[crayon-67ffbc1898989932084062/]
and
[crayon-67ffbc189898d380709035/]
99% percent of the errors should be gone.
If you like to stay with FluentAssertions (which I do not recommend), open your .csproj file and put brackets around the version. This will prevent you upgrading to version 8
[crayon-67ffbc189898f441540616/]