Quote: "what are the codes for this?"
Why do you think you read the tutorials? To learn how to code.
It's not good to start off big... like a 3D shooting gun demo.
Anyways, you can't expect a gun model to magically appear before your eyes. You could probably Google "gun model," and you'll get a thousand results of free gun models.
If you want to make a game, read the tutorials, start off small with a basic 2D game (like a Pong clone), and you'll get better. Judging from what you've been saying, I don't think you actually read the tutorials; you probably skimmed through them.
You can't make a complete 3D shooter in 30 minutes, even if you are an experienced coder. It'll take time, and if you go through it slowly, you can be very successful. But don't get crazy now, everyone here was a beginner also, and was in the same frustration as you: anxiously wanting to make a game.

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