Justinian's army conquered northwestern Africa, much of Italy, and southern Spain.

yes Africa does have an army.

It main strength at the beginning of the Punic Wars against Rome was it's navy. When Rome developed it's own navy, the Carthaginians recruited it's army from Spain, North Africa and northern Italy, with a strong cavalry arm.

No, Africa is not part of Spain.

Spain is a country in the continent Europe. Africa is a different continent.

No, the strongest army in Africa is Egypt's army.