Leaking Shower Faucet: Exploring Solutions for Hidden Installation with Photos

Hello.
I apologize in advance that the topic is not 100% compatible with the topic of this subgroup, I have not found a more appropriate one.
The case concerns the shower faucet - it is leaking, water drips when closed. This is a slightly less popular solution, as part of the installation is hidden in the wall under the tiles. Here are photos of this battery , or rather its part responsible for opening and closing the water, I managed to pull off the handle. The problem is, I don't know how to open it. As you can see in the photos, inside there is a plastic ring with teeth "tilted" to one side. The outer, metal sleeve inside has probably 3 "grooves" in which theoretically one could insert the appropriate key.
Can such batteries be opened at all, and if so, how and can anything be done about them after opening? In classic taps, you can simply replace the gasket, or is it similar in this type of tap (I've never opened one before)?
Thank you in advance!

Thanks for the answer.

Do I need a special key?
If so, do these plastic teeth need to be "twisted" or the outer part?
Can someone open something more or less similar ..?

I did not want to start a new topic because I have quite a similar problem. I have a classic bathtub faucet. The battery is dripping slightly. I wanted to replace the valve under the tap, but they can't pull it off. There must be a rock there and the tap just "stuck". I replaced the hot water tap without any problems. Anyone have any idea how to pull off the cold water tap? He doesn't want to do anything by force so as not to tear the battery off the wall

Yes, I turned it on. The hot water tap went down although there were also problems. I pissed WD40, waited a moment and downloaded it. But the one from the ground one sticks terribly tight: /

Do as I do.
You sit down on the bathtub, rest your leg on the faucet, and with your hands you grab the tap and pull it with all your strength.

Or, remove the battery and use a striker to treat the head while holding the knob

Screw on the nut (or screw - there are 2 types of fastening) and, pulling the knob firmly towards you, hit the nut vigorously with a small hammer.
If the head is old - sealed with a flat gasket, put a newer one on the o-ring, the whole cost is about PLN 5.