adopted dog is agressive

I adopted a 3-year-old dog from Harris county pets over the weekend. Everyone at the shelter said how sweet the dog was and when I saw him in his kennel he was quiet and was not barking.

I adopted him and took him for a walk and he lunged, barked, and growled at every human and dog in sight. I had someone come over and he almost bit them.

I am a 110lb woman and the dog is the size of a full-grown German Shepard probably bigger, so when he lunges I have to use all my strength, with the leash clasped around my waist, to keep him from getting away.

I cannot keep a protective aggressive dog, but the shelters are all saying they do not have space and i cannot take him to a shelter out of the county because they are all residents only.

I am not sure what to do.