It could be the brakes, but most probably the front control arm bushings are shot. Inspect them for cracks. Original rubber bushings give out periodically; replace with urthane for better handling and longer life. Also, torn dust boots on the ball joints indicate need for replacement.
Re: Car shakes when I brake only between 90 to 80 km/h
Your control bushings are done man. However, braking from 90-80 downwards must be done firmly in order to stop the shaking and to brake safely (Try that). If not, then your front rotors are warped.