Besides Bayer needing to win their games, they also need Bayern to start losing their games, because the difference between them now is 6 points, that's a lot, in fact Bayern can lose two games and still keep the first position because they have a better goal difference. And although Bayern have bad games, they are still strong enough to not allow a losing streak and lose the advantage they have now.
The chances are very small because even if Bayern Munich loses, it is not certain that Leverkusen can get full points in the remaining matches. Six points is a big number in the Bundesliga because maybe not many teams can make Bayern Munich lose luck in two matches. Leverkusen needs to make changes next season if they want to compete with Bayern Munich in the title race.
Bringing in some additional quality players can help them compete and this needs to be done by management if they want to chase several trophies next season because without quality players it is difficult to repeat the success of the previous season.