Hey, I think this movie is fairly recent, from around 2015/2016. I saw a trailer for it in late 2016. I think the language was German and the storyline was about parents living in a house and looking for a teacher/carer for their son who is made out to be a little child, 8 or so years old. The teacher arrives and gets to meet the son. It’s revealed that the son is indeed an older man (around 30 or older) who wears childrens clothes and is treated as child by his parents.

Thanks to anyone who can solve this