Freiburg soars into fifth place
Krmas rose above Fortuna's big men to head in a corner in the 87th minute to break the deadlock.
Freiburg's win allowed it to move past Mainz into fifth place on goal difference.
Earlier Sunday, Mainz held on with 10 men to earn a 1-1 draw at next-to-last Augsburg.
Adam Szalai scored for Mainz in the 43rd minute, connecting with a cross from Junior Diaz to drive the ball with his right foot past Augsburg goalkeeper Alexander Manninger.
Mainz was reduced to 10 men in first-half stoppage time, when teenage forward Shawn Parker was given a red card for rough play.
Augsburg got the equalizer from Sascha Moelders, who headed in a cross from Marcel de Jong. Despite having more than 80 percent of possession, Augsburg could not find the winner and now has three points more than last-place Greuther Fuerth.