How to clean my Burberry wallet

[babyconan]

I got this wallet from my friend, i just used it for 2 weeks but the back of wallet appear black dots, i tried many things to clean it but hopeless, any suggestion plz help

 

[Bubble_Bubble]

I have a Burberry shoulder bag of the same material and it becomes blue when my jeans brush it, so I clean my bag with a cotton impregnated with water. The Burberry shop assistant gave me this directions and they are only for the Burberry checked synthetic material (don´t wet the leather rims).