Hi Alireza,
Perhaps you're putting too much pre-spray down. When I first started I thought more pre-spray is better than less so saturated carpets.
I now know less is better combined with good agitation (especially using a portable, we havent got anywhere near the suction recovery of a t/m).
I now use the least ammount of pre-spray as possible (enough to be effective & stay damp through dwell time, aggitation & extraction, then rinse at as lower psi as possible to achieve good results.
Normally one cleaning pass then several dry passes is enough with man made fibres. With wool & wool mixes a couple of extra dry passes are required to leave as dry as possible after extraction as they will retain moisture for a LOT longer than man made fibres.
Carpet drying times is dependant on so many factors, fibre type and construction, depth of pile, the weather, level of soiling, power of machine, fresh air passing through room (windows open), use of air movers, the list goes on......
Hope this helps.
Jason.