Boxers

I recieved a BOXER pup,who is now 2 1/2 years old... NOW.
I took him from a lady that had the Brindle mother and two brindle and one black and white, She wasn't supposed to have dogs in her APT., SO,She kept them in a disabled car out back. And that is where she smoked coke or crack or whatever, so the landlord wouldn't smell it.
My dog has problems with learning. I had to work for 1 1/2 years to get him to sit,down,and shake hands. I used to train dogs in a few weeks for attack !! !! )
Is there any hope for him to continue learning ? I'm an EX horse, command dog trainer,and personal protection dog trainer,and now disabled. I've had hundreds of dogs.Mean,angry,fearful,etc. This dog will run around the yard,and into a tree. BUT I STILL LOVE HIM !! Melody.
Coppertop_46036@yahoo.com