Power steering rough idle and stall

I had started making payments on my truck listed above 1500 from my boss. He had taken it to the shop and had a bunch of work done on it to give to his son who which didn’t want it. I then bought it thinking everything should be up to date and a week or two after the purchase I noticed squeaking from the power steering pump when I would make turns. I added some fluid with stop leak and the problem went away. I then noticed that the check engine light went on and I didn’t have time to get it read because of the amount of hours I work. So then I noticed that low speeds it would idle weird and sporadic and even a few times shut off. So I immediately took it to the nearest auto store and had it read. It came up as power steering and that he didn’t know exactly what kind of power steering problem it was. So I did research because I don’t have the funds to take it to a mechanic and I’m mechanically inclined enough to do things. So I figured that it may be the power steering pressure switch. So I went back to the store and bought it and replaced the switch and I still have the problem. Does anyone have any suggestions?