Complex sentence: He took it to a New York art gallery where he sold it for circa 15 million CFA, while there; another American Warren M. Robbins, an arts collector saw and recognized it from his visit to Cameroon and raised an alarm.
Split into simpler sentences: He took it to a New York art gallery where he sold it for circa 15 million CFA. While there, another American Warren M. Robbins, an arts collector saw and recognized it from his visit to Cameroon and raised an alarm.