It looks really sick, mabey you can get them to give it to you. Or for a reduced price.Let them know that you have experience with tortoies and you can get it proper care. Poor little thing...
It's impossible to tell the health condition of this tortoise by the photo. It's clearly not a very good photo. And a single photo should not be used to judge the condition of the tortoise. I would ask for more photos (better focused ones would help).
What species of "African tortoise" is this supposed to be? I think I would find out a lot more information before deciding whether or not to purchase the tortoise.