If the copy works, at that point you have installed Audacity.
How are you executing Audacity, exactly?
Did you try Audacity can't open [SOLVED] - #3 by Gale_Andrews That is likely to be the easiest way to solve the problem.
Assuming you have not already changed the Audacity temp folder, the error suggests that you can’t access /var/folders/. Unfortunately, Audacity crashes or freezes if it can’t access the temp folder it expects. So another solution would be to check you have access to that folder. At its simplest you can do that by right-click or control-click over var/folders/ then Get Info. Click the lock symbol and give your password to make changes.
Gale