MacBook Pro motherboard failure and high charges

I am using a mid-2014 model mac pro retina. I chose the phone and computer for the strength and reliability of the apple brand. But first I had to make a paid change to my phone and now my computer's motherboard is malfunctioning. Unfortunately, I am asked to change the motherboard by Apple. I'm educator in Turkey. In this pandemic period, it is not possible for me to buy motherboards by giving the mentioned figures. And I'm sure these malfunctions are not user errors. I would like to contact an authorized person who will help me seriously in this matter.

[Edited by Moderator]