Who is the first libero in Germany football?

Interesting question!

There's a difference between "sweeper" and "libero". The sweeper was a defensive central defender without marking duties. His task was almost entirely defensive. The sweeper (Ausputzer) was usually very good in the air and strong at tackling. The libero was more a very withdrawn playmaker-type with very good reading of the game and passing skills.

The question who the first libero was is easily answered: Franz Beckenbauer. Beckenbauer's new style of play was a sensation. With sweepers it is harder to say who was the first. The mentioned Lothar Geisler was one of many sweepers in German football during the 1960s. It's hard to say who was the first among them. It was a gradual development when the WM-system was slowly replaced by the 4-2-4 system. That change began in the early-1960s and ended in the late-1960s. The sweeper system was already played in the 1950s (in other countries). It rose to prominence in the early-1960s when Inter introduced the cattenaccio system of four man-marking defenders who were backed by a non-marking sweeper. In Germany, that system was called "Doppelstopper". The "stopper" was the center half in the WM-system who was marking the center forward. In the WM, there was only one central defender (the "stopper"), but when the sweeper system took hold, he was joined by a second central defender (the sweeper) and hence it was dubbed "doppelstopper" (double stopper).

About Lothar Geisler it has to be said that Dortmund's stopper/sweeper was Wolfgang Paul, a very traditional center half type of player, not much of a libero. Geisler certainly wasn't a libero in the "modern" sense of the word, either.

 

The distinction between the roles of the sweeper and the libero is an important one, as the two tend to get muddled together in English. Just like Gregoriak said, the sweeper is a defensive specialist mopping up between or behind the marking defenders. The primary concern were through balls ( Schnittstellenpässe in German ), because at the time there were no one, two, or even three central/defensive midfielders preventing them.

In both the WM and the classic 4-2-4 the two nominally central guys were link-up players and nothing like a double pivot in modern football. The closest equivalent today would probably be the shuttle wingers in an attacking 3-5-2 just doing the same job a few yards closer to the centre of the pitch.

The libero role otoh was pretty much specifically created for complete and just overall superiour players like Beckenbauer or Matthäus. It is a free role, like what was given to some number 10s later on, just with somewhat less attacking focus. The libero always joined the part of the team in need of one more guy, no matter if that was the defense, the midfield or the attack and that is why only very complete players would work in that role. It is also the reason there have only been a handful of good liberos in football history and the libero never really took root outside of German football. Calling it a withdrawn playmaker may be selling it a little short, with all due respect to Gregoriak. Pirlo is not a libero.

Philipp Lahm could have been a good libero I guess, Michael Essien pretty much was in his heyday, I can't think of many other players in contemporary football who would qualify though.