In other love stories, they show the guy & girl falling in love then confessing. But it's different with SaGa because they've loved each other since childhood so they don't need to show them falling in love. They just need to show Sagar realising that he loves her (Gangaa already has) and he realises this when he thinks he is going to lose Gangaa forever.
The story isn't moving fast, it's just that SaGa's love story is different from the usual love story. Their fight to be together is the main plot since she is a child widow. ❤️