12V Leisure battery and wiring installation

I apologise that this is in English. I moved to a Norway from Australia six months ago and it is difficult for me to explain this in Norsk. My girlfriend and I just bought an Iveco Daily 2004 van, and we are converting it into a Campervan. We want to be super careful with this part so we believe it’s best to leave this job for the professionals! We would like to set up two 12V 250ah AGM batteries so that they charge off the engine whilst driving. We would like this set up so that it’s safe, with inverter, fuses and main switch. We plan on installing 6 lights in the roof, a 12V water pump, a tankless water heater (will use gas), 12V TV, 12V Fridge/Fryser. We would also like to have some wall sockets to charge a laptop and to use some appliances that require a wall socket.