The wing-back moved from Ajax three years ago.
He told FOX Sports: “I have developed super well in the past two and a half years. My English has of course also improved, which is always beneficial.
“I didn’t go to Chelsea with the idea of breaking through. I listened to my father. He told me to look where I could best develop in the next three years.
“In the first year I had a hard time in the beginning. I didn’t speak English, didn’t know anyone there. After four or five months I felt a little more at home.”