How real the documents are I don't know but they are part of the millions that were apparently leaked that has put pressure on Maureen and Ronnie for their tax shenanigans.
"The documents show Ozil earns a basic Arsenal salary of 10.2million euros a year. He gets 1.8m euros for each season the Gunners qualify for the Champions League group stages plus another 1.2m euros a year as a signing-on bonus. On top of that, Arsenal pay an additional 1,476,095 euros a year to his Dusseldorf company Ozil Marketing GmbH — which owns his image rights — as part of an agreement that they would pay him a guaranteed annual salary of 8,077,000 euros net of tax. £12,529,000 a year."
Quite a bit of dosh. It makes sense because all player contracts run through an amortisation process. There are documents knocking around online but again, we have to take these guys word they are real. No reason to think they aren't really.