It's good that you started by turning on View > Grid, and View > Snap to Grid. The problem is that the Pencil is at 20 pixels. The Pencil tool needs to be set the size to 1 pixel. You can choose any Foreground color, but I usually start with black for the outline of the shape. Zoom in to make it easier to see the grid. You could draw directly with the Pencil tool, but I find it easier to first draw a path with the Pen tool. As an example I've drawn a simple shape: With the path selected, in the Paths panel, choose Stroke Path. And choose the Pencil tool. If you want to enlarge the image, choose Image > Image Size. It is important to choose Resample: Nearest Neighbor. In the screen capture below I'm enlarging to 400% which means that wherever there was just one pixel, there will be 4 pixels. Hope this helps. If you have questions, let me know.
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