OK, feedback #1: Do an old man a favor: check your scanning software, I am certain there is somewhere a button that let's you adjust contrast and brightness. Rip up the contrast to 100%, the page will probably turn white when you do that, then lower the brightness until the drawing reappears.
Ideally you should chose a bright enough paper and a dark enough pencil, so that isn't always necessary and you can control the amount of contrast you want while drawing and don't have to always mess around with it while scanning, but the combo of dark paper and timid lines makes it really hard to see, what you are even doing for a pair of old eyes.
The lines, that I do see look like you are on a good trajectory. You are focused on finding essential lines that show the gesture, and design and execute them cleanly and confidently, and you even know how to exaggerate the poses for quite a bit of extra swagger.
I think you are at a point with your short sketches, where basic beginner advice reaches its limits, and you have to make some artistic decisions about where you want to go next as an artist yourself.
If you want to start really celebrating your lines, and keep to a caricature style, you could try switching to an ink brush. Pentel GFKP Japan worked best for me, not too expensive and reliable ink flow. Ink brush gives your line weight a lot of variation, (which might take a few attempts to get used to, but you'll figure it out) which will make your good line quality really apparent to the viewer.
If you want to go photorealistic instead, it's probably time to read up a bit on theory about how light and shadow works, and get used to doing longer drawings.
Another step into the wild would be to come up with short stories or jokes and try to do short series of three panels with a continuous narrative, to get used to drawing from imagination. Your foundation in drawing from observation should serve you well, but it is still a separate skillset.
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