The Van Amersfoort Racing driver lost control into the Lisboa bend before flying over the barriers and into a photographers' bunker at high speed.
"Just wanted to let everybody know that I am fine but will be going into surgery tomorrow morning," Floersch wrote on Twitter.
Floersch released from hospital after horror crash
"Thanks to the @fia and @hwaag_official @MercedesAMGF1 who are taking great care of me. Thanks to everybody for the supporting messages. Update soon."
VIDEO: F3 driver Sophia Floersch survives horrific airborne crash
Japanese driver Sho Tsuboi, who Floersch crashed into, was taken to hospital with back pain.
Race organisers confirmed two photographers and a marshal were also in hospital.
Pole-sitter Daniel Ticktum was leading the race when it was stopped.
F3 driver Floersch vows to return after horror crash