Fortuna's direct approach paid off as Schahin and Ken Ilsö struck either side of Reds striker Mame Diouf's equaliser to earn the promoted side a handy three points.
Ilsö warmed the palms of Ron-Robert Zieler just five minutes in, but a pair of uncharacteristically errant back passes almost gifted Hannover's Mame Diouf the opener.
The Senegal international rounded Fabian Giefer, only to see his low drive go the wrong side of the upright, before that man Schahin rose at the other end to head home his first Bundesliga goal since Matchday 6 and his fifth of the season.
Hannover have conceded more goals (eleven) from balls into the box than any other side in the Bundesliga, but it was a tactic that almost got them back on level terms early in the second half, with Giefer only just beating Ya Konan to Konstantin Rausch's hanging left-wing cross.
The Reds had offered little of note as an attacking unit, but when it came, Diouf took his chance with aplomb, killing Manuel Schmiedebach's pass on the chest and rifling home his second goal in as many games. A similarly emphatic strike saw Fortuna restore their lead, as Ilsö smashed home a stunning free kick to secure the win.
Line-ups and statistics