Hello,
This is a gaming PC. So, despite its 90 kWh battery, I don't think you'll be able to use it for more than 4 hours in the office without plugging it into the mains and deactivating the 4070 GPU.
And in games no more than 2 hours. But I don't use it for office work. So it's just an estimate and a personal opinion.

Good, but don't forget to disable the GPU 4070 using the armory crate application. Otherwise I don't think the PC will last 4 hours.