How to understand if the performance of a portfolio is good?

I’m starting my journey in the realm of personal finance and I stumbled across this interesting piece of software :wink:
Now, what I’m trying to accomplish is to understand the performance of a portfolio. It’s not clear to me.

I downloaded all the transaction data of my investments, I cleaned it and I imported it into PP.
I read on the forum that the performance section is dependent on the time horizon. Indeed TWRR and IRR changes a lot modifying the start date. Numbers seems good but I do not understand the theory behind it.

I would like to better understand how to evaluate a portfolio.
Could you point out some reading?
What should I look for? Indicators like TWRR?
I would like to compare it to a dummy portfolio. Is that possible? does it makes sense?