帮我检查一下英语作文有什么语法错误的地方.
This afternoon,I went shopping with my mom.While we walking around in the shop.I saw a foreigner in men's department.He wanted to buy a pair of shoes,but he couldn't talk to the salesgirl,because he couldn't speak Chinese,the salesgirl could't hear English at all.I knew it's very difficult for the foreigner to buy his shoes like that.So I translated for them .At last the foreigner bought his shoes and said thanks to me ,my mother also praised me that I gave a hand to the foreigner.So I felt very happy.