That was be very hard. Firs way it to risk 10,15e and go to mi community ,I can give you person who can flash your ROM with authorized account..
The other way is to open back cover and EDL point. To be able to get connection between PC and Mi flash tools..
Try to do some research and in mean while I will try find this contract with authorized and send you Pm.
The third thing is service centar but I did recommended you.. they will literally restore you phone and in the end they will do.
I bad have bad experience.
So I seat ,two weeks exploring and if you read carefully,you will learn and fix your phone.
ALL YOU NEED TO READ CAREFULLY AND WRITE DOWN IMPORTANT THINGS.