Garantiert Zeichnen Lernen -
"Garantiert Zeichnen Lernen" (Drawing on the Right Side of the Brain) by Betty Edwards is widely considered the "gold standard" for anyone who believes they "can't even draw a stick figure."
: Take a complex line drawing (like a portrait), flip it upside down, and draw it that way. This forces your brain to see lines and shapes instead of "a face." Garantiert Zeichnen Lernen
If you want to dive deeper, you can find the latest edition at major book retailers like Ernster. "Garantiert Zeichnen Lernen" (Drawing on the Right Side