Hello friendly plumbing people! I live on 1st floor of 6-floor apartment building. Recently the drainage has become so loud from the other apartments above. We have a central stack that runs through the bathrooms but I hear it coming through my showers drain for some reason.... like a hollow gurgling at first then hiss then the obvious draining away of water. I use the shower all the time so I don't think it would be a dry P trap..? I tried to research the stack plumbing type we have which led me here but I'm not au fait with this level of plumbing. Now a few months ago, I left drain cleaner in for a bit too long (ostensibly) and the centre piece (name?) shifted sideways. I pushed it straight again with pliers but couldnt take the grate off. (pic attached) So basically im wondering if this is my fault and need to fit a new trap or it is a problem where my waste pipe meets the building stack. Any suggestions would be appreciated. Thanks in advance!