Hi, I am a senior VR app developer.
I have plenty of experience in developing VR app.
So, I can complete your VR app for Cardboard as well.
Please check out part of my VR apps.
https://www.freelancer.com/projects/unity-3d/Hospital-Room/
https://www.freelancer.com/projects/iphone/Picture-with-play-video-app/
https://www.freelancer.com/projects/rendering/HTC-VIVE-virtual-showroom/
...
If you want a good result, Please feel free to contact me anytime.
Best Regards.