I live in a small room and believe me when I say it is really impossible to separate the two (I live in a poor house, there is not much space). How do I go about doing it? My old cat generally have this harsh attitude towards people and other cats. And there is a new cat coming in a few hours. Should I separate their food and get them a separate litter boxes? What else should I keep in mind if separating them in a few days is impossible?
Update: Hello everyone! I've read all ur responses. It's been 5 days since I made this post. Just a little update, I managed to make a small space for the new cat with all her needs: bed, food, toys, her litterbox (dw, they're further apart to where her food is). It's a difficult situation for me, her litterbox is literally beside where I sleep. But during those 5 days, I've exchanged their sheets to get them familiar with each others' scents, I've made them see each other between the door and get them distracted with toys. The hissing became less apparent. I wanted to keep on doing these for a few more days but due to my carelessness, yesterday, I forgot to close the door and my old cat came in. They started chasing after each other, but there was no hissing/growling. I still keep them separated, I don't think they're 'that' ready yet, especially my new cat. It is a bit stressful for me but I'm not giving up. The new cat was given to me, FYI. I don't plan on giving her back because of her history of being abused by her previous owners. I don't want to stress the cat as she had been rehomed many times. And we've become a bit comfortable with each other now.
Anyhoo, thank u for ur responses! :)