SBR Time Pressure

Hi All, I have problem with organizing timing with SBR. I gues I try to put all the explanations similar to model answers by ACCA and also revision kit I study, which does not seem possible with given timing. May I ask your general advise about how wo approach explanations, especially regarding calculations? For example, if I am asked to provide explanation and calculation for goodwil, shall I first explain goodwill as per IFRS 3 in general, or is it okay to just explain the steps of calculation briefly? Because the biggest time I spent in mocks are the group questions as I mostly spent close to double of time given(mark per 1.98) , and I was not able to decrease it significantly even I do question quite as fast as possible. Therefore I gues the solution is decreasing explanations.