On 14 May 1938 a copy of this poem was printed in the Austrian weekly Agrarische Post, under the title ‘Denke es’. It was then falsely attributed to Adolf Hitler.
In the Hitler biography of John Toland (1976) it appeared for the first time in English translation. Toland made the mistake in identifying it as a true Hitler poem, supposedly written in 1923.
That poem was not written by Hitler.
According to this website and other reputable-seeming sources, the German poet Georg Runsky published that poem, “Habe Geduld”, around 1906.