My parents come into my apartment as if it's theirs. Is this normal? What should I do?

I mean, it is theirs, but I don't think that's how it works. They live in a house that they've built and when I got into college, in my 3rd year, they bought an apartment as a long term investment, in which I could stay how long I want, by myself or with my SO. So yeah, it is there, but I still have a right to my personal space, right?

They come about once a month to visit me, announced but not invited, they come in while I am sleeping or in the shower and argue with my why wasn't I ready when they arrived. They go through all my stuff, saying that they are cleaning, they move all my things in different places, throw away or take home my things, saying that they are trash, and in the end we fight because of all of this and they keep telling me that they are going to kick me out if I dare to say one more thing in their home. It takes me about a week to find my stuff in all the mess that they've left and to put everything where it was supposed to be.

To better understand what I mean when I say they go through my stuff, I don't mean they just open my drawers or cabinets, they take out all my clothes and everything that I have in my drawers or wardrobe, to sort them and to see what they could find. And it's not like I have anything illegal to hide, but it's annoying to see them look for and find my condoms or receipts from restaurants or for different things that I've bought.

I feel like, even though the place is legally theirs, I should still have a right to privacy and personal space, right? From what I understand, if I were to rent a place, the owner wouldn't legally have the right to do any of this. But what legal rights do I have over my parents in this situation? What can I do? I haven't finished college yet, and the place where I currently work doesn't pay me enough to even cover rent...

Updates
6 mo
Nice talk doesn't work. I tried explaining them that I want my personal space and my privacy, and that I have a right to that in my place, but they keep arguing with me that it's not my place and that I have no rights. I was thinking of getting a restraining order for them, would that work?

My parents come into my apartment as if it's theirs. Is this normal? What should I do?
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