the activeSelf property is read-only. Perhaps you want ‘.SetActive’.
For future reference, please use code tags: Using code tags properly
Please post the actual error next time, instead of just saying there is one (also where it is… not too hard to guess this time, mind you).
I’d suggest that you try referencing game objects in the inspector, rather than always relying on GameObject.Find (withTag). 
Lastly, though not impossible (maybe?), the compiler - and its warnings/errors - are probably more accurate than your guesses.