Can my boss fire me for being slow? As I do have disabilities.

Assuming you are employed, I recommend that you notify your employer that you have a disability and that you need accommodation in the form of more time to complete certain tasks, as an example. You should provide a medical note to support your accommodation request.
If you have already been fired, then please give us a call to discuss your entitlements and the most efficient way to recover what your former employer owes you.