I read this article and as I am not a pilot I don't really understand what the pilots did to resolve the issue to the problem. Would you be able to elaborate please.
They didn't do anything to rectify the issue.
The aircraft centre of gravity has defined limits, to ensure that the controls have enough authority to actually control the aircraft. If the CofG is too far aft, you get the situation that happened to the 747F in Afghanistan, when full forward stick could not stop the nose from rising, and placing the aircraft into a deep stall. If it's too far forward, you'll emulate the MCAS 737 flight paths.
During flight, it changes as the fuel is burnt. On smaller aircraft that change isn't all that great, but on large aircraft, with tail tanks, it can be quite large. The loading has to be done in such a way that the CofG remains within the defined limits at all stages of the flight.
When calculating the take off data, one of the numbers that is extracted is the take off trim setting. That's the setting that the entire tail plane will be set at, to give you the correct rotation and control forces at rotation. If it is miss-set, then, at one extreme, you'll be unable to rotate, whilst at the other, the aircraft will try to rotate without any control input, and before you want it to. Both are dangerous.
In this instance, there were a couple of effects. The CofG was much further forward than calculated, so the trim setting was incorrect, and therefore the aircraft did not want to rotate. The 'cure' of more power and go faster, increased the elevator's authority, so that it was able to override the nose down CofG, that should have been removed by the trim. Once airborne, the automatic trim system of the aircraft will move the tailplane, in an attempt to neutralise the need for the elevator input. Basically, it will apply a load of nose up trim. As there was enough trim available to do this, from that point onwards, the aircraft would feel reasonably normal.
But, because the trim is actually out of limits, and remains so, the control authority would be dramatically reduced, and this would become increasingly evident as the aircraft slowed and nose up trim was normally required. As didn't run out of authority, they didn't notice this effect, but they were actually in substantial danger for the entire time.