Re: how to reduce cpa without losing conversion?
It's a good question but certainly the answer is not a single liner
There are certain step which you can take to reduce the overall CPA for your account:-
1. Pause or remove all the non-performing keywords from time to time.
2. Keep an eye on the converting queries regularly and add them as keywords so that chances of getting more conversions are high in future, which directly impacts the CPA for your account. At the same time, add irrelevant terms as negative keywords.
3. You might want to explore Conversion Optimizer and try that as well. You can define the recommended CPA and try to improvise more conversions as well.
Also read this article on improving ROI for your account:- https://support.google.com/adwords/answer/2375509