Imagine a musician (pianist, guitarist etc.) who is learning a new technique, or a new piece of music or song. Musicians learn by going slowly at first and gradually speeding up as they become familiar with the technique or music.
I recommend the same when you start preparing for IELTS, or when you learn a new exam technique or study a new topic: start slowly. Try to achieve the score you need at slow speed, and then gradually reduce the time until you can do the same at exam speed.