I think the question how to understand Nietzsche’s Wille zur Macht („will to power“, „will to the might“ ) can mainly be answered by his personal and philosophical development, and - last but not least - by his language use, and his language was of course German. Nietzscche was a philologist, a poet, and of course a philosopher.
By the way: the German word zur is a composition which includes two words: the prepostion zu („to“) and the article der („the“), in this case der is not masculine, but feminine because of dative singular. Thus der Wille zu( de)r Macht is „the will to the might (power)“.
Philosophically Nietzsche was a pupil of Schopenhauer, and this fact should not be confused, if it is said there were two or three or even four or five stages in Nietzsche’s life:
(1) childhood and youth,
(2) from his youth till his „terminated contact“ with Wagner,
(3) from his „terminated contact“ with Wagner till his „Zarathustra“,
(4) from his „Zarathustra“ till his collapse,
(5) from his collapse till his death.
Philosphical interested people interpret (probably correctly) the 2nd, 3rd, and 4th stage as the main stages in Nietzsche’s philosophical life. The most Nietzscheans say that the „terminated contact“ with Wagner was the most important change in Nietzsches life, but that’s wrong. This „terminated contact“ wasn’t as much a terminated contact as it is often interpretated.
And we don’t have to forget Nietzsche’s desease because Nietzsche had been ill since a certain time. Probably was this one of the main reasons for his success - he himself often mentioned it, and many of his philosophical explanations are based on medical, physiological, especially immunological, and of course psychlogical aspects. He won or gained more or less of these aspects because of his pain, I think.
Nietzsche was perhaps a pan-immunologist, a pan-immunological philosopher, in any case a „life-philosopher“ (Lebensphilosoph) who had learned by his teacher: the „life-philosopher“ (Lebensphilosoph) Schopenhauer.