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This is a fancy example where the roof sticks out to provide some shade.
https://sommerhaus-piu.de/ for more pictures.
No idea if they built more than their 3 models not far from Berlin, but those are jealousy inducing. -
Awning sounds like a good shout, however my only gripe with it would be that you will miss out on the direct sun in the winter which is obviously useful. I'd try find a best of both worlds option if possible. Retractable awning perhaps? Or even a cantilevered parasol out in front on the deck that you can swivel around to block the sun on really hot days?
I'd go with an awning. If you want to get fancy, make a permanent one with wooden slats that only shade at the right angle of sun. Plus, can you have windows on both (or even 3) sides to maximise airflow?
Shed heat problems aren't just from the window IME, more the small overall space and heat through the roof - you want to get any breeze available flowing through from any direction.