Fix webbapp that was built one week ago

I've had a freelancer on here building a webbapp and finished his work 1 week ago. The APP is a webbapp and suppose to work on all devices, I only had access to Android and Windows and I assumed the APP also worked on iOS. Now it shows that the APP don't work on iOS very well and the freelancer is now ignoring me. I am looking for a freelancer to debug and fix the APP so it works with iOS too. [About the APP] The is built for conducting job interviews online/by distance by using our interactive APP. The person being interviewed is given questions to answer and each question is recorded and then the whole interview is uploaded to "backoffice" for us to watch and rate the people applying for a job. We have built the APP so I can wholesale this to other companies who needs to conduct online job interviews. There is these following three profiles for this app. [Super admin] We have a super admin where I as the owner of the APP can create new "admin user". Each admin user has their own login for back office and have their own LOGO and their own name. This means I can sell this as a wholesale solution to other business. [Backoffice] This is where each "business/admin user" can view the job interviews, create new questions and other misc stuff. [Frontend] This is where the user/the person who's being interviewed visits. We send the user a link/URL via E-mail for their interview. They sign up their name, phone number, age, email and also take a "selfie". This means that the webbapp needs access to the users camera and microphone. This seems to be the major problem on iOS devices. It mostly works fine on Android and Windows but pretty much never on iOS. Here's a link for the frontend for you to test out. [login to view URL]