Bathroom drain has very dirty – any ideas on how to clean it?

We have a fully tiled bathroom on an upstairs floor, I have unscrewed the drain cover and inside there is a mess of grime – looks like white foamy stuff and probably hair etc. When we have a shower sometimes the soap comes out of the drain cover like dishwashing liquid bubbles. I’ve tried Draino but this didn’t work, today I found little midges (insects) in there.