'Germanic' groups like the Vandals and Visigoths were, historians almost all agree, mutli-ethnic groups composed of recruits from a variety of backgrounds. Many of the Vandals would have had ancestors from across the northern frontier (what the Romans called 'Germania'), but they also certainly would have picked up recruits from other parts of the Roman empire before they conquered Africa.

We know less about the Vandals than we'd like to, and much of what we do know is based on unreliable autors who drew heavily on 'barbarian' stereotypes that clash with available archaeological evidence. But the narrative we have says that the Vandals settled in Spain for 40 years before resettling in (and conquering) N. Africa. During those 40 years, the group's initially multi-ethnic character would have had a long time to further change as any 'Germanic' soldiers and their children married locals, and as some of the Vandals' Roman neighbors decided to join Geiseric's retinue.

By the time the Vandals settled in N. Africa, they were so Roman that almost no traces of 'Germanic' art or material culture can be found to evidence their presence. This cultural assimilation into Roman society was probably just as thoroughly reflected in their demographic constitution; having spent two generations away from the northern frontier, the N. African Vandals were likely Germanic in little more than name.

We might be able to say more if we had evidence for the Vandals as an intrusive cultural group (say, people in Tunisia being buried with a foreign/intrusive burial rite, or separate cemeteries in which the conquerors preserved distinctions beween themselves and their Roman subjects). The abscence of this evidence makes it very difficult to say anything about cultural distinctions between conquerors and conquered; and indeed, the lack of any trace of auch distinctions suggests the Vandals had become so Roman as to be materially identical to their Roman neighbors.

follow up question: Are there any traces of the Vandal population left?

Another follow up question: What was the Vandal Kingdom like? Did they maintain the Roman infrastructure? Also how many Vandals actually settled in North Africa?

In 442, the Vandal king Gaiseric instututed some sort of major reorganization of the Vandal social and military structure (subsequent Vandal kings dated the beginning of the “Vandal era” to this year). Up to that point the Vandal army may have still been based on a traditional tribal warrior-aristocracy, but afterward both military rank and land ownership were distributed by the king to his personal followers (who were thenceforth known as “chiliarchs” based on the newly-created Vandal military rank).

As for the native North Africans (i.e., the Moors), their relationship with the Vandals ranged from ambiguous to hostile. Procopius describes a telling incident during Belisarius’ Vandal campaign: the general was approached by representatives from several Moorish groups asking for imperial recognition of their leaders. The status of Moorish leaders within their own societies had traditionally been based on Roman recognition, which they’d been unable to obtain under the Vandals. The Vandal kings had tried to replace the emperors in this role, but there was apparently some dispute among the Moors as to whether the Vandal king was a legitimate substitute.

From this we can gather that the Vandals had attempted to maintain the same relationship the Romans had established with the Moors (which included mutual military support), but weren’t very successful. According to Procopius, they overwhelmingly sided with Belisarius against the Vandals during the war.