The cushion is not washable in a washing machine and should not be drowned in water. Use special cleaning (seen down below).
Textile cleaning in spray form.
Bonded leather is most appropriately treated regularly (3-4 times/year) with products aimed for PU and Bycast.
When dust starts collecting at the bottom of the sheep skin you should regularly vacuum and dust off the cushions. This makes the wool rise again and get more voluptuous. Use a glue roll for loose visible dirt. Spots should immediately be washed off, otherwise they risk becoming permanent. Clean the cushion by hand with a sponge, lukewarm water and wool shampoo that you get at the retailer store of furniture.