Second shedding phase while I use Propecia and Minoxidil at 8 month. Should I increase the Propecia dosage from 1.25 to 2.5 mg?

This needs an in-person evaluation. I suggest seeing a hair loss expert now to evaluate and go over your condition and provide you information about your best treatment options. There are great non-invasive options like prp/progesterone and/or hair transplantation. See an expert. Best, Dr. Emer

It depends, each case is different. No, increasing from 1 mg to 2.5 mgs daily won't change or improve the results, I will suggest you to book a consult with your hair loss specialist for further evaluation and for comparing the baseline photos vs 8 months photos. Good luck.

With your problem, I would go back and meet with the doctor who prescribed you the finasteride in the first place