What is the best way to track unique and overall clicks at my newsletters
I would suggest checking out https://support.google.com/analytics/answer/1033867?hl=en as it will help you build a link you can put in your newsletter that when clicked takes the person to whatever page you direct them to, but has analytic code built into the link so that you can track how many and how often it is used. Total sessions and unique users will both be tracked.