[Mailanka]

You're a beginner, right?

Sure, don't sweat the climax. Look, a climax is a great thing. Moving your story forward, with a direction in mind, culminating in some awesome reveals, then winding up loose ends and giving your campaign a satisfying ending will leave your players satiated and pleased. I certainly have a very good experience with that sort of thing.

That said, play's the thing. I've seen people, especially novices, ruin their games because of "climaxes." They have a premise ("There was a murder!"), a climax/resolution ("the butler did it!") and an arbitrary length of time that they think the campaign should last ("this should go for 12 sessions at least! Maybe years!") and you end up with session after session of no movement as the GM hedges his meager inspiration for the "Grand finale" that never comes because the players give up. Or worse, the players go in a direction the GM doesn't expect and so they derail his plot and he either has to abandon his climax (and go back to square one) or drag them kicking and screaming back to his plot, which is known as "railroading."

So as a beginner, I think you're better off avoiding thinking too far ahead. Instead, operate from the principle of "Awesome now, not later." Introduce totally cool elements, study the art of making this session awesome, and worry about campaign structure later. Yes, your stories will eventually wander and then crash, but you can't expect perfection your first time out. As you master the art of a good session, you'll start to see how structure works, how you can segue one session into the next, and how you can keep the story on track while acknowledging the contributions of the players, and then you can start to worry about overarching structure. But for now, think smaller and deal with more immediate, important GM skills. If every session is fun, your players will keep coming back, even if the grander picture isn't that great. Building a long-term plot is more of an advanced skill (and some GMs don't even bother to cultivate it, preferring to let the pieces fall where they may, then look them over and see a way to thread them all together to retroactively create a plot and give the game a rousing finale).