Maya, mine are a 39 1/2 and I usually wear a size 9 Narrow U.S. Is there any chance you can get to a Nordstroms to try them on first IRL to assess the comfort and fit before buying them on Ebay? When I bought mine at Nordstroms my salesman said I could return them no questions asked if I wasn't happy with them. I know you don't have that option on Ebay.
(Can't be sure if I sized down because they don't come in narrown)