Complex sentence: The partitioning powers (in particular, Russia) demanded that the Sejm passes further reforms, with the intent of strengthening their power over the Commonwealth, and the original commission was allowed to work till January 1774, extending the Sejm which was adjourned again.
Split into simpler sentences: The partitioning powers (in particular, Russia) demanded that the Sejm pass further reforms, with the intent of strengthening their power over the Commonwealth. The original commission was allowed to work till January 1774, extending the Sejm, which was adjourned again.