So, with the number of remaining matches only 7 more matches, with a point difference of 6 points, and with a GD gap of almost half, it is quite impossible for Leverkusen to be able to take over Bayern Munich's position in 1st place. So, this is like the end of Leverkusen's achievements this season, just being a club in number 2.
Great observation, mate. Apart from the fairly large points gap in the remaining matches, Bayer Leverkusen also has a slightly smaller GD than Bayern Munich, which makes it seem like their difficulties are even more difficult. There's no chance for Bayer Leverkusen now & Bayern Munich's task is to quickly confirm that they're champions of the Bundesliga, it's like the scudetto in Serie A.
Of the 3 games you mentioned, I only see 1 as a difficult game for Leverkusen. Mainz vs Leverkusen, Mainz are one of those teams that we rarely discuss here without realising that Mainz can always beat the top teams when Mainz are at home.
I've no doubt that Leverkusen can beat Mainz even though it will be a tough fight for them in the next match, from the 3 matches I mentioned before, I only doubt that Leverkusen can beat Borussia Dortmund, you know that Borussia Dortmund has a good squad, right?