u/Low-Outside1600

Any advice would be appreciated

My bathroom in my apartment doesn’t seem to be vented properly.

When I flush the toilet the shower drain makes a sound like it’s sucking the water away

if I turn on the shower it takes a few seconds for it to get the air out of the shower head and almost pulsates for a few seconds

If I use the sink you can hear the same noise the toilet makes from the shower. My concern is it smells bad from the shower and also assuming this is a health hazard. We try our best to make sure all the traps are filled up so the smell can be contained but doesn’t seem to help all that much. I believe the plumbing is not vented properly.