Complex sentence: Fifty G.91 R/4 aircraft were taken up from a cancelled Greek/Turkish order but being unsuitable for operational use were used as training aircraft and were operated solely by "Waffenschule 50".
Split into simpler sentences: Fifty G.91 R/4 aircraft were taken up from a cancelled Greek/Turkish order but were deemed to be unsuitable for operational use. Alternatively, these were used as training aircraft and were operated solely by "Waffenschule 50".