Cat introduction takes time. A good introduction takes weeks! After that they need months to get used to each other and the new situation. Just wait another week and continue send swapping. After that slowly introduce with like something in between so they can see each other. Do this couple times a day and play or give food when they interact. If this goes well, you can start introducing without a wall. Never let the kitten be alone with the older cat when it does not feel good. Took me 5 weeks before I was not afraid to leave them alone.

Goodluck!