He is welcomed by his orientation demon, who shows him around and explains how things work. The engineer notices that a lot of things aren't working and are in dire need of fixing. The air conditioning is busted, the network is overloaded, there's power shortages everywhere, everything is overheating. He mentions this to the little demon and suggests he could try to fix things. He also had a few ideas about redesigning the place to make it more efficient. The demon takes him to Lucifer, and Lucifer is enthusiastic about the whole idea and gives his permission.
A few months later God decides to visit Hell for an inspection. He is greeted by the new renovated Hell and he's absolutely speechless! The corridors are now well lit and properly ventilated. The air conditioning is working and the thermostat is fixed. The elevators are working again. There's no more loud noises of grinding and screeching coming from all the machinery. The lava spill has been contained. All the horrible fumes are now gone and the denizens of Hell use electric cars to travel. There's even a monorail being constructed. The electrical grid has gone geothermal. Cell coverage was full and there was even wifi. Not only that, but several clubs were under construction and there was already a kick-ass pool with attached jacuzzis. Some bulldozers were building a beach and a tropical-themed resort nearby. The condemned souls were enjoying their time playing sports in new gyms, walking in parks, racing with muscle cars, playing video games and doing all sorts of other activities.
God furiously works to Lucifer's office, kicks the door open and walks in
"What the hell is going on here Luci?"
"Well we got an engineer and he fixed the place up for us"
"You can't get engineers. Our contract clearly stipulates that all engineers belong with me in Heaven."
"Well too bad, I'm not giving him over"
"I'll take you to court you ungrateful bastard!"
"Ha, good luck finding a good lawyer up in your Heaven!"