Complex sentence: Later, Narimanov became a teacher in a private pro-gimnasia in Baku, where he founded the first public free-access library and reading hall, which became a cultural center of the entire Transcaucasia.
Split into simpler sentences: Later, Narimanov became a teacher in a private pro-gimnasia in Baku, where he founded the first public free-access library and reading hall. This became a cultural center of the entire Transcaucasia.