For some context: This protest took place in the context of the Rosa Luxemburg conference, which is a yearly event organized by the newspaper "junge Welt". As they reported, multiple participants of the protest were heavily injured, including broken bones and a life threatening injury of an elderly man (German interview with a paramedic). As far as I can tell, the injured policemen are, unfortunately, not in a life threatening situation. The headline that they are injured is probably only right wing propaganda.
That is not true. The Lenin-Liebknecht-Luxemburg Demonstration has been a thing since 1919 to honor the deaths of these revolutionaries and has been a big state event during the existence of the DDR. It's independently organized by revolutionary organizations from all across Germany. The Junge Welt and the Rosa Luxemburg Konferenz has only been a thing since 1996 and is something completely different that happens on the same weekend. Both the RLK and Die Linke (left non-revolutionary socdem party) are somehow trying to claim this event.