Answer: shut off the water supply, empty the flush, remove the water supply, then unscrew the flush tank.
Corner WC models are very practical in small rooms, because they save precious space. However, being rarer than the others, spare parts are more difficult to find. Better to go to a specialized brand. The main malfunction of a flush, whether corner or not, is the water leak. The problem can have several origins. Either the water overflows from the tank, in this case the float no longer works and must be changed. Either the water flows inside or outside the bowl, in this case it is necessary to replace the valve opening mechanism or the foam seal. To change the entire corner flush, shut off the water supply and pull the flush to empty the tank. Then unscrew the water supply, then remove the flush tank (which is often fixed via a bayonet system to the tank). Then replace it with the new one. You too, send us your brico question