Vauxhall Astra problem with asta h (faults 050074,161450,161600.)

Hello, Good evening, I have an Astra H 2008 model van with z17 engine imported from england, I have bought this around 6 years ago, And it's always garaged, And i always disconnect the battery from the van When i bought it, It had 70K on the mileage now after 6 year's of barely being used it has 71K mileage. Now i have a problem that in Malta, Nobody can resolve it, Even the agent in Malta. When i connect the battery and start it it works fine after around 15 minutes of being driven the cluster of the dash starts flickering and the front lamps turn on automatically and I'm unable to turn them off,They turn off only when the van is switched off When i turn on ignition again the cluster doesn't turn on and no power is given to the ignition even with the ignition on ,Then i found out that when i put on the front lamps the cluster turns on,Everytime i turn off the van this is repeated, for it not to do this i have to disconnect the battery and reconnect it again and still after the first time i turn it on after around 15 mins the cluster starts flickering again and the same problem with the headlamps. When i made the pedal test i got these results: 050074,161450,161600.In Malta nobody can get a handle of this and i was told something like this was never seen.I would appreciate if i can get some help towards this problem Thank you for reading.