It looks like the bike has a unique sliding rear dropout.
It also appears to have a single cable housing the entire length from the bars to the IGH hub. That likely could be used with a derailleur cable, although the long housing would be suboptimal.
For the droput, I'd really consider fabricating a new right dropout, or perhaps welding a derailleur hanger to the dropout. A "claw" and vertical dropouts would be just a mess.
Or, you could contact Focus and see if they sell derailleur style dropouts for the bike.
Oh, some come with a belt drive, and some with a chain drive. A belt would be a mess with shifters. A chain drive might be OK.
Anyway, I'd agree with others... WHY? There are millions of hybrid bikes out there already with standard derailleurs. What would the Focus give you that another bike wouldn't?
If you already had the bike, that would be one thing, but you're wishing to buy it as a project bike for which you still have to acquire a wheel, cassette, derailleur, shifter, perhaps new brake levers, new chain, and new cables and housings. Plus acquiring or fabricating the derailleur hanger.
That is a lot of work for a project bike.