Arduino not recognizing when a timer reaches 0
As per comment and Majenko's answer you are current creating local variables called secLeft and secLeft2 inside the 'if block.  These take precedence over the ones you have defined globally.  Removing the in declarations from inside the if block will stop doing that and point you at the globally defined variables.

As to the rest of the code. If you have 

secLeft=(secLeft2--);
secLeft2=(secLeft);


Then that translates to this sequence of instructions


Assign secLeft with the value of secLeft2
Decrement secLeft2
Assign secLeft2 with the value of secLeft


And in the end you do not change anything.

This is because you are using post-decrement on secLeft2  EG secLeft2--.  This is a feature of C style languages.

I am not sure what you are even trying to do at this point.