Trouble replacing a toilet cistern button

[OM2]

We've got a Villeroy and Boch toilet
The cistern button has been faulty for a few years
30% of the time when pressed it gets stuck

I've looked up instructions on how to replace on youtube
This button seems to be different to others

Can someone tell me what I should be doing to take off and install a new one?
I'm guessing I can just get a universal replacement button?

See below for a pic of the existing

 

[Elkato531]

The whole button should unscrew anticlockwise. Send a photo of it to
https://www.toiletspares.co.uk/
Or better still, replace the whole flush assembly with

Fluidmaster Push Button Cable Dual-Flush Valve - Screwfix