I'm Microsoft Certified Developer Professional, offering services as Full Stack Developer (Frontend & Backend), having hands-on experience of developing small, medium and enterprise level solutions over the years which included complex solutions (ERP, financial Domain, Healthcare domain, Learning services Domain, Ecommerce domain, Legal Administrator etc.) for more than 10 years now.
As per word- you are using the Graph API for the MS-365 authentication. I would like to discuss your requirements in detail to understand the complete scope and then propose a realistic timeline