want to get back to dark brown..help!

Ok I am a hair dresser. The universal rule of color is "color CAN NOT lift color" You cant put brown over black to lighten it. Heres the problem with lightening. The color that you used may have matalic salts in it. If you put bleach over it. IT WILL MELT YOUR HAIR. There are strippers. Please go to a pro to have this done. And if you bleach it your self. Be sure to do a test strand in case you do have salts. And finally. If you lighten it yourself, go to a beauty supply and buy professional prducts. As well as for color. The reason that the box stuff doesnt work right is because it assumes the color you have, and it lift you MORE then you probably need to go with HIGH ammounts of ammonia, then forces pigments in your hair. So hence after you lighten it, The box color will lighten it even more and then die it. If you go to the beauty supply get 20volume and bleach/ the color of your choice. Chances are you will have to wash it out and re-apply. You can get a shower cap and use a blowdryer to speed up the process. No matter what you do your hair is gonna be fried. Best bets are let a professional like me fix it. And after be sure to use protien and moisture packets to reconstruct whats left. Happy tinting and good luck.