30 minute drawing.

Thanks for sharing! It's great you're trying to do studies.
You seem to be focusing on details too much, while your proportions and the feeling of form and anatomy are not quite there yet. All the details (tattoo, beard, detailed hair) would look better on a drawing that is built right. I'd recommed doing more 30-60 second gesture drawings, and watch videos of how masters do it (Glenn Vilppu is great). It might seem impossible at first, but you'll get the hang of it, and with time your anatomy and proportions will be better. The purpose of such short 30-60 second sessions is to stop picking out details and be able to capture only the most important parts of a human figure.

The expressions are drawn in a very interesting way, but the focus of the image seems scattered. Human instinct for interaction tends to focus more on the eyes, so you could add more detailed steps around the eyes (such as deepening the eye sockets, the upper eyelids, darkening the pupils, etc.). Also, deliberately outlining the contours of the face on the left side of the image feels a bit abrupt; to differentiate between hair and face, it's enough to convey this through black and white contrast. The back of the head and the top seem to be missing a portion, so next time you could first draw the skull structure of the head and then add hair on top. If this drawing has a reference photo, you can also place a nine-grid reference line on both your paper and the photo to compare and make adjustments.表情画得很有趣，但画面的焦点似乎分散了。人类互动的本能倾向于更多地关注眼睛，所以你可以在眼睛周围添加更详细的步骤（如加深眼窝、上眼睑、加深瞳孔等）。此外，故意勾勒出图像左侧的脸部轮廓感觉有点突兀；为了区分头发和脸，通过黑白对比就足够了。后脑勺和头顶似乎少了一部分，所以下次你可以先画出头部的头骨结构，然后在上面加上头发。如果这张图有参考照片，你也可以在你的纸和照片上放置一条九格参考线，进行比较和调整。