i just want to ask what you mean by "long time"

1. there are 2 action that can be used to deconstruct parts:

dismantling [crowbar] - you need to look from the inside of base building object, this action will return materials
destroying [sledgehammer] - you need to look from the outer side of base building object, this action won't return any materials (it will only destroy selected part after longer time)

This is intentional (previously there was a bug that you could build gate with hammer). Now you need pliers to build a gate construction part.