Wohlfarth was most recently at Wehen Wiesbaden in the third tier of German football and previously played for Bayern Munich reserves in the same division.
County revealed former Hamilton and St Mirren player Corcoran had "left with immediate effect". The 32-year-old made four appearances in August before being hit by a groin injury and has only played once since.
Manager Derek Adams previously brought in Ivan Sproule and Evangelos Ikonomou, who made their debuts in Saturday's 4-1 win at St Mirren, and is awaiting a work permit for Canada international Andre Hainault.
Adams told the club's official website: "Whilst we knew we had to add to the squad, it was important that it wasn't just numbers - anyone we bring in has to add something to what is a great group of players already at the club.
"We've had to cast the net far and wide to achieve that whilst working within our budget but with Ivan, Evan and now Steffen I think we've proved that it is certainly possible."
At the same time it has been confirmed that Mark Corcoran has left the Club with immediate effect. All at Ross County thank Mark for his contribution during his time at the Club and wish him well in his future career.