Sorry, I cannot look at your VI because I don't have LabVIEW 2021 here. Consider "save for previous" to get more responses.
should i use case structure ??
Why a case structure?? Yes, you could use one, but there are plenty of ways that don't need one and these solutions are probably more elegant.
Did you look at some of my examples in my earlier link?
As I said, do a "save for previous" so I can look at the VI.
(From the gigantic oversized picture you posted (please crop it to the interesting parts!!!) you need to continue with the basic tutorials because that code makes absolutely no sense. For example, you compare a red and a green diagram constant and these are never equal, right? So what's the point? Where do you define the loop rate? Why is there even a while loop because since the subVI is outside it will only run once once and then never again, so the values in the tunnels will never change.)