Room tension

So, I (20 m 🇵🇱) moved back to my house, but unfortunately was left with no room. The backstory is: I shared a room my entire life. First with my mom and then with my sister. My things for a very long time used to be in the living room. Then my sister moved out for 3 years and I sort of had my own room. I couldn't do pretty much anything with her things, so my things were just laying on the floor. One day she came and took and donated her stuff, so I could finally put mine into the wardrobe. Then, after she broke up with her boyfriend we returned to sharing a room.

Now, recently I have tried moving to Spain for university. I have agreed with my sister, that she could claim my room when I move out, and she bought a double bed for her and her boyfriend. Thankfully my family kept the bunk bed we slept on. Unfortunately, the flat where the room I rented was very disappointing, but I tried staying here to combat my homesickness. One day, when I was in that room, I've heard domestic violence in my landlord's living room. I felt absolutely scared and fleed back to my family house where everyone was happy for me to return safely (including my sister). But there was a problem: I no longer had a room. We only have 3 bedrooms (my mom's, my brother's and my sister's (used to be our shared bedroom).

Currently I'm sleeping on the couch and keeping my stuff in the suitcase. I don't want to go back to Spain, as all options are out of my reach, and I don't want to share a room, as it constricts both me and my sister. I could afford some kind of renovation, but there is no way we could add another room or even a new wall.

I really don't know what to do. Sorry for all the yapping.