skin-deep
Only on the surface; not having any deep or honest meaning; not really or closely connected with what it seems to belong to.
Поверхностный, неглубокий.
Mary's friendliness with Joan is only skin-deep.
Ralph crammed for the test and got a good grade, but his knowledge of the lesson is only skin-deep.
He had a skin-deep knowledge about this issue.
У него были поверхностные знания по этому вопросу.