Little update;
A couple of days back I found out that my High-beams were not working although on the dash they were on. They replaced the relay and said it was corroded (.....I thought I bought a NEW van)

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Anyway the problem with the immobilizer probably comes from the fact that the whole fusebox/relaybox is corroded. They ordered a new one but it will take some days. So hopefully the van will start the comming days.
Strange problem for a new van.
I also noticed when driving 165 km/h that the speed is not constant. It will drop to 163 km/h then to go to 168 km/h again and this like a cycle over and over again.
As they say it doesn't have a limiter they think this as well can be the corroded fusebox/relaybox as it might give spikes in power.
When I get back from holiday I hope the parts are in and all the problems are gone.