Last week Hertha Berlin beat Stuttgart by 2-1 and not Mainz but yeah, maybe it doesn't really matter because in reality even though Hertha Berlin is at the bottom of the table but Hertha Berlin still has the ability to win too. So yes, playing against FC Koln is of course an important match too, because based on the head to head record it looks like Hertha Berlin has good dominance when Hertha Berlin plays against FC Koln.
I don‘t believe that Hertha BSC can win the game. The win against Stuttgart last week, that was good for motivation, but Stuttgart is not an extreme good team in the Bundesliga. I wouldn’t compare them with FC Köln, they are a better team at the moment, they won against Leverkusen last week. Today there should be three points for FC Köln and then there are only two match days left in this season. There is also an anniversary today: Florian Kainz is playing his 150th Bundesliga match today.