i got new cat and my old cat is extremely scared from him
i got stray cat home, i took care of him and now i decided to make him friend with my old cat coz he been alone for 8 years already, and i want friend for him. so i put him in different room to take care of him for almost 3 weeks, and let them meet only a bit to eat food together, and then separated, and now i am trying to make them friends.
the huge problem is, now when the new cat is trying to play with my old cat, every time he is near him my old cat SCREAMS and hissing, and starting to attack him and run away. i cut their nails, but my old cat is just so scared of him and getting so angry when he's near him, and usually he is extremely friendly and so loving, and the new cat is also extremely nice, and only wants to play with him but he is so scared that he thinks he wants to attack him and he screams non stop. the advices i got from people around are to just let them be, and they will take places in the house and slowly become friends.
from here, i got advice to watch videos and work according to them (which i tried) but it doesn't work because my old cat is so scared.
what should i do?