I used this code to copy one 2D array to another 2D array:
Array.Copy(teamPerformance, 0,tempPerformance,0, teamPerformance.Length);
This is correct:
Array.Copy performs a shallow copy, so the instances of arrays inside the inner dimension get copied by reference. You can use LINQ to make a copy, like this:
var copy2d = orig2d.Select(a => a.ToArray()).ToArray();
Here is a demo on ideone.