You could have the characters part ways amicably, realizing they have different paths in life. Maybe they express mutual respect and gratitude for the time spent together.
Maybe let it end with a bittersweet moment that shows growth and acceptance. For example, one of them moving away for a better opportunity, but they promise to remember the good times.
You could end it with a poignant moment where they both understand that the love has run its course. Maybe a heartfelt conversation where they express their gratitude for the time together and accept the need to move on. Or, have one of them make a selfless decision for the other's happiness, even if it means ending the relationship.
Well, usually in a novel, a character behaving in a crowd would pay attention to their body language and facial expressions. They'd avoid being too loud or drawing unnecessary attention. Also, they might follow the flow of the crowd instead of going against it.
You can end a conversation by introducing an external distraction. For example, a sudden noise or event that forces the characters to stop talking. Or maybe a character gets a call or text that they need to attend to.