Ng click and Ng tap and app performance

Hello there,
I have a project that I have been working on it for months. Two problems persist that I cny work it out are my buttons aren’t picking when user is clicking or tapping in it. It gets slower as if user clicks on it too much. Also the whole app looks lagging and there is a slight but visible different between 8.1 across to 9.1 iOS.

Can someone suggest what can I do to improve performance and find out why Ng click or Ng tap are not picking up??