The Bundesliga's Tuesday night games taught us three things.

We conclude the first half of the season with an English week in the Bundesliga. While Bayer Leverkusen defeated Mainz, Eintracht Frankfurt overcame Freiburg, and Wolfsburg easily defeated Borussia Mönchengladbach, Borussia Dortmund fell to Holstein Kiel in the early kickoff.

Borussia Dortmund should start spending more money:

Which names come to mind when we consider the Dortmund team and the guys you could see playing for a victorious team: Karim Adeyemi (on his day), Jamie Gittens, Nico Schlotterbeck, Serhou Guirassy, and Gregor Kobel? That should be plenty to tell you.

Unless Dortmund, like Leverkusen, makes wise moves in the transfer market and invest in their squad's lack of winners (a mentality issue), their full-back's lack of quality (a long-term issue), additional center-backs, and dependable creative players, they are not good enough to contend for a Bundesliga title in the near future. These should all be long-term solutions, not six months into the new season when they realize they have a problem and sign players on loan in the winter for a temporary solution.

Stopping the purchase of mediocre Bundesliga players and adopting more daring team planning and spending strategies would help with most of this.

Bayer Leverkusen appears to be invincible:

Mainz was going to be a challenge for Leverkusen because they were flying high and had already caused issues for Dortmund and Bayern Munich this season. All that matters is that Die Werkself got the job done, even though they required an incredible free kick from Alejandro Grimaldo to win. Leverkusen controlled the ball and gave Mainz numerous chances, but they were unable to convert them because Patrik Schick was having a bad day. With the victory, Bayern has once again closed the margin to one point before their match against Hoffenheim tomorrow.

You may be asking yourself, what did we learn?

Like an unstoppable freight train, Leverkusen keeps doing what champions must do to win the tough games; it may not be pretty, but it does the job. Unlike some teams that wear black and yellow, you never get the impression that they shot themselves in the foot after winning the championship the previous season. This implies that Bayern's ability to avoid mistakes will probably determine the outcome of the title battle. This Leverkusen team is a different breed from the Bayern team of the past, who typically make mistakes but it doesn't matter because Dortmund has already made a mistake.

Omar Marmoush will be sorely missed by Eintracht Frankfurt:

The incredible season Marmoush has been having is beyond words. The Egyptian may have played his last game for the team before joining Manchester City, recording a goal and two assists. This performance demonstrated the weight of his creative burden and his significance to the side.

The main uncertainty surrounding his departure is whether someone will be able to step up and at least shoulder some of the burden, or if Frankfurt will need to make another wise transfer acquisition. Hugo Larsson (5) and Mario Götze (6) both produced more opportunities than Marmoush in this match.

You can ask me what I think about Marmoush perhaps moving to the city. Given the history of Frankfurt attackers leaving Deutsche Bank Park, I believe it may be career suicide. The Egyptian will need to adjust to Pep Guardiola's style of play, and the nature of City's style of play will also prevent him from playing to his full potential. Furthermore, it would be foolish of City to pay Frankfurt's demand, which is reportedly around €80 million after just six months of this form.

To wrap out the second half of the season, we (I) shall return tomorrow for the Wednesday games.