First Critique!

I did some five-minute sketches, and I'd like feedback on them. In particular, I feel like my proportions are off, and some poses (especially the less dynamic ones) feel kind of flat. But I haven't been doing this for very long, so any feedback/advice at all is welcome! I know I don't see all of my own issues :)

https://imgur.com/a/1efu16I

I actually think your sense of proportion is pretty good. Some bits are off in the heavily foreshortened areas, and those require a lot of attention and repetitive practice to get right. But the muscle simplification on the arms and legs looks clean. Some of the poses could look flat because there are subtle angles in parts of the body that you have to make sure to capture. For example, the hips and ribcage could be leaning forward, leaning to the side, leaning back.  I'd recommend you try to act out the poses yourself and be thinking about what position the parts of your body are in, how much pressure they feel, how balanced you are etc. Then go back and try to draw the pose while capturing what you noticed. 
Hope this helps, sorry for the ramble

Siento que las líneas están un poco estáticas, las figuras se sienten estaticas , mas como una estatua qué como si estuviera apunto de moverse, aun asi la figura humana está muy bien hecha y las proporciones se sienten familiares:)

Hi! It’s really great that you got back into drawing poses — it definitely shows 
You have a good sense of gesture, which is a big plus. Sometimes, though, it feels like when you start adding forms, you stop following the gesture line. Try first blocking in simple volumes along the gesture (for example, think of the ribcage as an egg-like shape), without focusing on details or pressing too hard with the pencil, and then build everything else on top of that.

It’s also nice to see that you’re thinking about anatomy, but it might help to simplify your approach for a while: build the body using basic forms — the head as an oval or a box, arms and legs as cylinders and spheres — always guided by the gesture.

If you feel unsure, do more quick gesture drawings with loose, confident lines that capture the movement. And most importantly, draw regularly, even if it’s just 5–10 minutes a day. Mistakes are a natural part of learning.

Try not to just mindlessly copy the reference. Observe it first, then draw (even from memory), and only after that compare and correct your drawing. Most importantly, enjoy the process, not just the result — that’s how real progress happens