Database
[{"_id":{"$oid":"627c4eb87e7c2b8ba510ac4c"},"name":"Müller","skills":{"languages":"English"},"birthday":ISODate("1989-11-02T03:00:00Z")},{"_id":{"$oid":"627c4eb87e7c2b8ba510ac4d"},"name":"Nelson","skills":{"languages":"Spanish"},"birthday":ISODate("1989-11-02T03:00:00Z")}]
Query
db.collection.update({"name":"Müller"},{$set:{"skills.languages":"Italian"}})