What are two quotes describing flash-forwards inHeart of Darkness, and why it is a flash-forward as it relates to the story? Can you explain to me why the following quote is a flash-forward as it relates to the girl or women at the end of the story? I laid the ghost of his gifts at lasts with a lie," he began suddenly. "Girl! What did I mention a girl? Oh she is out of it—completely. They-the women I mean—are out of it—should be out of it—We must help them to stay in that beautiful world of their own, lest ours get worse. Oh she had to be out of it. You should have heard the disinterred body of Mr. Kurtz saying, "My intended" You should have perceived directly how completely she was out of it. Please explain this flash-forward as it relates to the girl/women at the end of the story and please provide and explain one other flash-forward quote in the story.

Before answering your inquiry about Joseph Conrad’s novella Heart of Darkness directly, it is important to establish two things.
First, the narrator of the story is not Marlow; it is an unnamed man on the cruising yawl who hears Marlow's tale and chooses to relay it to the reader. Remember that Marlow has not prepared this story in advance. He tells his tale informally and haphazardly. The narrative is broken by flashbacks and flash-forwards, and it is laden with randomly interjected musings, thoughts, and reminisces in a way that mimics how real stories are told. This non-linear plot structure is a primary reason why Heart of Darkness can be such a struggle for many readers inexperienced with Conrad’s style.
Secondly, Conrad wrote Heart of Darkness in a style called Literary Imagism, which attempts to replicate the experience of a character for the reader. The narrator of Conrad’s novella was mystified by parts of Marlow’s narrative himself and was burdened with the thematic importance of the story. Conrad attempts to communicate that confusion and burden by forcing the reader to feel it themselves. With those two points out of the way, let’s move to your question.
I cannot reference specific page numbers because I do not know the anthology you are using. However, I can provide you with some clarity regarding the specific flashback you mentioned and offer some other options for you to provide to your teacher.
You quote Heart of Darkness when you ask about the flashback below:

I laid the ghost of his gifts at lasts with a lie," he began suddenly. "Girl! What did I mention a girl? Oh she is out of it—completely. They-the women I mean—are out of it—should be out of it—We must help them to stay in that beautiful world of their own, lest ours get worse. Oh she had to be out of it. You should have heard the disinterred body of Mr. Kurtz saying, "My intended" You should have perceived directly how completely she was out of it.

This interjection by Marlow is an example of the non-linear way the story is told. At this point in the story, Marlow hasn’t even met Kurtz yet! The fact that Marlow jumps to the Intended foreshadows her thematic importance of his lie to Kurtz’s Intended, and it shows that Marlow is reflecting on his choice throughout his narration. Remember that Marlow chooses to tell Kurtz’s Intended that the ivory trader’s final word was her name. In truth, it was the famous lines, “The horror! The horror!” Marlow is arguably complicit in Kurtz’s misdeeds by participating in a kind of banal cover-up of the truth.
There are dozens of other options you could select for the second example of a flash-forward in Heart of Darkness. Marlow mentions specific details about his meeting with Kurtz several times before he reaches the Inner Station in his narrative. One notable example occurs just a few lines after your example when Marlow muses,

Everything belonged to him—but that was a trifle. The thing was to know what he belonged to, how many powers of darkness claimed him for their own. That was the reflection that made you creepy all over. It was impossible—it was not good for one either—trying to imagine. He had taken a high seat amongst the devils of the land—I mean literally.

This flash-forward hints that Kurtz isn’t only a “remarkable” man, as told by the Chief Accountant at the Outer Station; he is also an evil one.