AR build in unreal engine 4 problem

I have built an AR App Book. And now apk. file is available but when I test some images, there are 2 problems that I need your help:
PROBLEM 1: when my model is rendered, that model is not close to the images. It must be manually modified to the position that I expect. But this action is incovinient. The model also has no shadow due to the environment lighting.
PROBLEM 2: I tested one model with one image but all of model are shown up when I turned the app on. I would like to have one set-up model shown up when I track one image.
I’ll appreacite for any suggestion or advice