Bayern Munich are back to normal, they scored exactly eight goals. This is the Bayern Munich we are used to. It would have been better if they had stayed strong like this at the beginning of the season, wasn't it a little late? Anyway, it was fun to put on a show like this. Mainz had a goal, it was a good goal, but afterwards Mainz could not reach Bayern Munich's half and could get into the penalty area, I am not very sure about that.
Are they not normal before this match? 
I'm not sure how you define 'normal or not normal'.I think they are normal, mate. They are just decreasing their performance this season. If they can win with big score against Mainz, it is because Mainz is just a weak team. You can see Mainz is a part of the teams in relegation zone. The quality of Mainz players is much lower than the quality of Bayern Munich players.
Today was Bayern Munich's show day and they destroyed Mainz badly. Harry Kane scored his 30th goal and he is not stopping.
It just proved that Bayern Munich has great attackers. And Harry Kane becomes the right machine goal for Bayern Munich. Sure, Harry Kane is unstoppable to be the candidate of the top scorer in Bundesliga this season. Yes, he already scored 30 goals so far.