Over the years I've been creating and maintaining the WopiHost project, I became quite knowledgeable in integrating with Office for the web (Office Online Server and Office 365) and in the specifics of the MS-WOPI protocol. If you need my help or expertise, I offer paid consultations for a fixed price of €250/hour. Or you can choose to sponsor the project on GitHub.
I'm also the #1 contributor for the
ms-wopi tag on Stack Overflow so you can try your luck submitting your question there or, if it's related to my project, submit a question directly in the repo or via Gitter. I try to help as I can.