Question

Hello Rabbi Michi! 
Wishing you a happy conclusion of Passover. 
 
My question is this:
How can one study Jewish law in depth? 
I’m not sure how much studying responsa is really a good idea. 
It’s just very strange to me that learned people who know how to deal well with a Talmudic passage still, when it comes down to practical ruling, open the Mishnah Berurah.
I’d like to try to get into the head of a halakhic decisor and understand how Jewish law is decided in, say, a contemporary issue.
But how can one study Jewish law in depth aside from the Shulchan Arukh and similar works? (Beit Yosef, Tur, Mishneh Torah, etc.)
Thank you for your time!