How to remove/change shower drain

[djm2121]

Hi everyone

Just looking to get some advice in regards to my shower drain that's draining slowly

Moved in about 12m ago and recently noticed the shower draining slowly

I've tried to remove the grate to get access an auger in there but haven't been successful. Tried leaving in WD40 at the rim, tried turning out out with pliers and hitting with a screwdriver and mallet. So I've given up on turning the grate and now considering removing and replacing the entire thing

At the moment, the square section of the drain cover appears to be surrounded by silicon and not grout. Is this as simple as cutting the silicon to remove the whole drain cover, get the auger in and clean the drain and replacing it with a suitable similar sized cover and silicon?

The dimensions of the square portion is 90mm x 90mm and I think the diameter of the circular section is 80mmdrain cover 

Pretty new to home ownership/DIY, so any advice or comments would be very much appreciated!!

Thanks!!