How to implement user activity tracking on web apps?

Question

I wanted to know user activity on webpage how much time a signed in user spends on a webpage and get data of how many people use the web app, and the most commonly used webpages.
Im not sure if i should use google analytics or build my own smaller version or use both.

Answer 1

https://www.sololearn.com/learn/PHP/1843/
A cookie?

Answer 2

I dont know much about using cookies so will look in to it. thanks