thanks all
@saadyj
nazir autos also told about same sensor but this other shop guy said it might get fixed with wiring only n it did n saved me extra 6.2k
name of shop was auto diagnostic center,its in G9 markaz at back of rahat bakery infront of some newly opened showroom
anyways today i went to GIKI n came back n by the grace of ALLAH ALMIGHY it was a fine trip without any issues what so ever MASHALLAH
when i opened bonnet after reaching GIKI to add more water in radiator's plastic pipe,it was already full :o 
also i came over my fear of driving it at 120 speed n kept it at 120 most of the time,sometimes reached 130-140 but kept at 120 to avoid challan
at one point i was overtaking a car that was going at 130 n while i was overtaking it,i saw speed camera :o
but when i had a look at cluster,my speed was 120 
temperature needle remained below middle all the time,didnt used ac at all though used just the fan while going