Visual Studio Bug system errors

Question

Alright so I'm taking a class for this, teacher cannot find problems with my code, happened on 3 different occurrences different problems. First problem has to do with creating a program and a class, though it seams in each file classes, methods, headers, are throwing "global namespace already defines something, or "name" already defined with parameter types, like the project isnt reading them correctly.
Second problem is where I have a file.txt, its named correctly as per class instructions, in the project file where it is supposed to be, and for some odd reason, "cannot find (filepath/file.txt)" I'm looking right at it, it isnt opened or conflicting. Using net.core