How do i free up population
There are a few things you can do to free up or gain population:
1) Upgrade Residences
2) Replace a residence with a Magical Version
3) Replace any pure culture buildings with ones that give culture and population
4) Make current any older chapter population culture buildings via royal restorations
5) Place and/or level up the Golden Abyss Ancient Wonder
6) Sell off any non boosted manufactories
7) sell off any excess boosted manufactories or workshops that you do not really need.
8) Teleport a workshop or manufactory into your storage and place it back at a later time when you have more population
I have not seen your city so I'm not sure which will work best for you, but these are a few ways to do it