Complex sentence: Seven years later, on 16 September 1787, he reached the rank of teniente, becoming in "ayudante mayor" on 5 October 1790, and, on 23 April 1794, he became a Captain.
Split into simpler sentences: Seven years later, on 16 September 1787, he reached the rank of teniente. Later, on 5 October 1790, he became in "ayudante mayor" and, on 23 April 1794, he became a Captain.