What are the goals pursued by Justinian, sending troops to Italy, North Africa, Spain?

By sending troops there, he wanted to free these lands from the barbarians. As we remember, after the collapse of the Western Roman Empire, its territories were captured by barbarians. So in North Africa the Vandal kingdom was formed, in Italy – the kingdom of the Ostrogoths, in Spain – the kingdom of the Visigoths. Nevertheless, the military campaigns of Justinian made it possible to destroy the barbarian kingdoms and liberate the lands. So the kingdom of the Vandals and the kingdom of the Ostrogoths were destroyed. We can say that Justinian was able to restore the former borders of the Roman Empire, his possessions did not include the lands of Gaul, Spain, Germany and England.