Museum of broken relationships actually exists in Zagreb, Croatia. It started out similar... Muzej prekinutih veza, Zagreb Croatia.
The song playing at the end of the film and over the credits is "Young and in Love" by Ingrid Michaelson from her 2019 album "Stranger Songs", which was inspired by the Netflix series, Stranger Things (2016). Dacre Montgomery who plays Nick, also plays Billy Hargrove in Stranger Things.
Selena Gomez is credited as an executive on the film. Whilst a producer is the key person in charge of production, daily operations, and overall getting the film made, an executive producer is someone who either contributed a large sum of the film's funding, or was heavily involved in promoting the film in pre-production.