After changing battery and display, the new display wont pop in housng

Today i started repairing iphone8p

After watching guides, videos and reading i was finally done after 3 hours.

Unfortunately now the new didplay wont sit in to the housing of the phone.

I found out video about cheap display having biggger buffer and thus not sitting properly into housing.

Unfortunately i didnt find out how to make it pop.

Could anyone help me out here?

Edit: i didnt remove the glue from first battery. Might this be a problem?

Edit2: i tried setting the buffer into the slot under the display metal cover which seems to be thicker than on original display from the display. Afaik it sits in the right place maybe little too low.

When i try to pop the display on one side it pops on the other and i cant make it stay.

Edit3: I've taken apart the display part, make sure everything was seated properly, reassembled, taped the buffer by the video cable to hold in place and the screen keeps poping out.