Step 6, should this read nut, these should be tight and sealed.
Lifting up cistern when full to check for water running down thread, and around siphon or flush valve nut.
Al
Usually you can lift off the decorative cover and find a screw head to tighten, hopefully the spring toggle nut will grip without having to slide wc forward.
Al
Click out the twice valve using clips on side
Try turning seal around or replace, look for tiny bubbles on rubber seal, if u see any burst with pin.
Al
It's a wirquin jolly I reckon
Attach it back onto button if you can and secure somehow
If u buy a new wirquin flush valve, comes with button, it's just a case of turning valve anti clockwise and lifting out.
Al