Repairing a Broken Sectional Back?

My neighbor gave me her sofa when she moved, but because of the small doors of our apt. they had to remove 1 of the sectional backs to get it through the door. Now it's broken even more.

I can't afford to get a new one and the other issue is even if I could afford it: our apts. are national landmarks so the size of the doors are the same width as they were back when they were originally built which makes it challenging to buy furniture that fits through them. It's an honor to be here, but a challenge all the same.

Anyway, this one has already broken a hole in our wall when it broke further when someone leaned on it too hard. I'm wondering if anyone knows if this can be fixed easily which I'm doubting or if you can refer me to a you tube video or website to show me how to try to rebuilt a sort of frame and make a new cushion. I'm a newbie, but I'm pretty good at catching on to things. Thank you to anyone who can help,