Setting up pivot tables properly for inventory tracking purposes

A bit of background:
I’m former military, and currently I’m the head of inventory at a fabrication company. While I was in the military, our inventory was kept mostly on paper, and everything that was annotated in excel was done using basic formulas and a single sheet.

I am using Excel on a work laptop and I would consider myself somewhere between beginner and intermediate level.

My problem currently comes from the fact that this company I work at never had an actual inventory system before, which I’m currently building from the ground up by myself. Since I don’t have extensive Excel experience, I struggle to materialize my plan and thoughts into this spreadsheet. Currently I have a master list, which I separated by location, category, item ID, and amount in stock and I’m trying to make a separate sheet with a pivot table that can show each shop independently whenever I click a dropdown menu. The pivot table I did make is a bit hard to look at and I can’t figure out how to make it do what I need it to do. Additionally, whenever I update a number on the master list, which is where the pivot table is sourced from, the numbers on the pivot table don’t update with the information. I should also mention that we have 3 different “shops” that we supply within our company, which is the main purpose for me wanting to figure out the pivot table. I’ve looked up some tutorials on YouTube on how to do these seemingly advanced things, but I can’t seem to find one that fits my specific needs or that explains how to properly do this.

If any of you have trouble understanding the issue, please let me know, I’m not very experienced with excel so I don’t know all the terms for everything

To summarize this wall of text:

Need pivot tables that I can separate individual shops through and update each shop’s stock individually.

I would love some help on this. Thank you in advance