Allow me to chime in here with a non-professional opinion.
The meager educational contact I’ve had with whatever semantic field the plot notion belongs to is limited to one –or two, maybe– lecture(s) about the “narrative arc” and certain standardized types of characters, as part of an otherwise technical course about (short) video-editing, plus one couple-of-month-long course about narratives in general, but not as much in the context of story-telling as in that of semiotics.
Plus, I’m no native, which may seem irrelevant, but I’m providing this background info anyhow, so you get an idea of how come, despite my otherwise good command of English, I have no real grip on how much the plot concept includes in its scope: My own lack of further familiarity renders it somewhat ill-defined. So, in light of that, I hope you don’t mind me speaking in other (and in my view more graspable) terms.
You mention that you’ve come to the point where you “no longer know how to go forward”. This statement should preferably be re-defined in terms of what point your character(s) have come to: At least one of them has most likely been facing some kind of problem, the severity of which is not really relevant. It is, perhaps, a commonplace experience for Western World citizens to have some sort of epiphany about how shamefully trivial their own predicaments are, compared to the life-threatening perils elsewhere in the world that they read about in the news, but a novel is not journalism. And that’s partly the magic of literature: how it can turn the trivial to thrilling. It may be a magic of disputable value, but it’s remarkable nonetheless.
Erk has already pointed out that structure-conformity is more decisive in movies than it is in [written] fiction. But let’s face it: it does offer certain “cheats” that can facilitate the aforementioned effect. Standardized character types, for example: protagonist, hero, antagonist, secondary characters that do not evolve, some deux ex machina, maybe. I’m not sure whether these are the same terms that are used in English texts about drama and narration theory, but the important thing is not to agree on terminology; rather to develop an understanding of the traits that define each type of character, function-wise.
I mentioned earlier that at least one of them is most likely facing some kind of problem: That’s your protagonist, right there. P, for brevity’s sake. If you want to go “by the book” (which will be my presumption for all “shoulds” and recommendations offered in this paragraph), the problem should be introduced after first having offered a somewhat “factual”, albeit fragmentary, perhaps, presentation of P’s identity. One chapter should suffice, just like five to ten minutes do in a movie. Then, as mentioned, comes the problem, which should gradually start culminating. This culmination should span throughout most of your story. Trivialities will do just as fine: Even my annoyance at not getting along with my neighbor can culminate into something unbearable. Of course, the focus may shift to other characters, or there may even be passages where P is entirely absent, but the reader/viewer should be… well… looking forward to hearing from him/her.
Whether or not your protagonist is also your hero is up to you. A hero is defined as having certain unchanging traits that somehow drive the story forward and, ultimately, contribute to the resolution of the protagonist’s troubles. Marvel’s superheroes, with their superpowers, is probably as close to a stereotypical example as one can conceivably come. In short, at the end of your story, the protagonist emerges as a “changed man”. The hero does not. What makes it even more interesting, though, is that these terms don’t actually refer to characters. They are mere functions, that can be either embedded into the same character (who, in that case, will emerge both changed and unchanged, depending on how you look at it), or allocated to different ones, as is the case, for example, in One Flew Over The Cuckoo’s Nest, where McMurphy is more of a hero, whereas chief Bromden is the actual protagonist.
So, have a look at your main character, and try to determine which of these two functions s/he serves. Or is it both? Even if your main character is just a hero, it is the protagonist’s culminating troubles that provide a time-axis, so to speak, for your story. In other words, an easy, “by the book” answer as to “how to go forward” is you go toward the resolution of whatever problem has been presented, be it trivial or severe; focal or, in less conventional structures, peripheral. Your main character, even if s/he is not the one facing the problem, should most likely play a part in resolving it. If that’s already done, then closing time is probably approaching. Just allow for some “breathing space” for a finish, where the reader can get a reassurance of normality having been restored, or perhaps even refined.
Disclaimer: The above should be read with a pinch of salt. And some popcorn.