It could be a 3" soil not a 4" soil,you can get a 3" pan connector which is made of a stronger plastic not like the more flexible multikwik,you are connecting new to very old so it is trial and error
You could get a 32mm bend one end fits onto the 32mm pipe the other end has a 1/14 nut that screws onto the basin slotted waste, then put an inline trap further down
