Uphill struggle

Pull the old pan connector completely out off the 4" pipe going into the floor, push a new one in down to 7" to the centre of the pan connector off the finished floor

 

Pull out old one, put in new one, if it's too long, cut it down

 

Looks to me without the wall, there's no problem, no need to cut anything.

Mr. HandyAndy - Really

 

from that new photo it looks flush yet says going uphil of 5 cm? Is the toilet pan UK model?

 

Tom that video is class

 

Have you bought a polypipe pan connector & pushed it down???

 

If the pan connector is too long cut it down man