Excel is not saving multiple sheets

Hi, I have a problem I've never had before.

So I was working yesterday on my MSc, I was putting different results into different sheets. I've opened it today and I had 1 (first) sheet only, the rest of them is missing. I was like okay, my bad, maybe I had some warning before, I've decided that I don't want to do it again so I moved to another one, 14 sheets, I've made it, saved, no warning, just question where to save. I'm opening it again and... only one sheet.

I have no idea why it's happening, I'm not new in using it but this is so basic and I don't know how to fix it.

First file was copy-paste from different excel files, not connected (I think)
Second one was imported from .prn files, thrugh power query (I don't exactly know how it works, it's on my to do list this year)

I just want to save my work so I can finish my freaking thesis

Also, I checked different files I was taking data from and they are unchanged