Add spaces: Bigapartmentof170m²whichsleepsupto8people.

Answer: Big apartment of 170 m² which sleeps up to 8 people.

Add spaces: TheunreformedleftistsformedaFrontdesForcesSocialistes(FrontofSocialistForces).

Answer: The unreformed leftists formed a Front des Forces Socialistes (Front of Socialist Forces).

Add spaces: Itwasinthismachinethatthefirstactual"computerbug"wasfound:amothwhichshortedoneofthe17000relaysinthemachine.

Answer:
It was in this machine that the first actual "computer bug" was found: a moth which shorted one of the 17 000 relays in the machine.