"To lose a fortune" means to suffer a significant financial loss, often referring to losing a large amount of money or assets that one had acquired over time. Full definition
This topic is a lot more complicated than what we can say in this blog, and you could gain or lose fortunes on real estate at the time of separation. (ylaw.ca)
During that time investors can lose fortunes for themselves and their families. (tradingonlinemarkets.com)
Before the film is over, Hope will find love, will find her father after he has died (and here the screenplay departs from the novel), and will discover her cold inheritance after losing a fortune in misbegotten gold. (filmfreakcentral.net)