<p>Why does Resharper want you to change most variables to var type instead of the actual type in the code?</p>

It's just an option. You can disable it:
ReSharper -> Options -> Code Inspection -> Inspection Severity -> Code Redundencies -> Use 'var' keyword where possible: change this to "Do not show"
There's also the context (lightbulb) option which will take you in each direction - this is under ReSharper -> Options -> Languages -> C# -> Context Actions -> "Replaces explicit type declaration with 'var'"