I know that drinking alcohol is forbidden, but is it true that if you drink it , your prayer is not accepted for 40 days?

Praise be to Allah, the Lord of the Worlds; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.

It is reported in an authentic Hadith that the Prophet (Sallallahu Alaihi wa Sallam) said: “Whoever drinks alcohol, his prayers will not be accepted for forty days.  But if the person repents Allah forgives him.  If he returns to drinking, then Allah will undoubtedly make him/her drink from the river of Khabal.”  The Prophet (Sallallahu Alaihi wa Sallam) was asked: “And what is the Khabal river?”  He replied: “The pus of Hell fire denizens.” [Ahmad, Al Arna’ut considered it a good Hadith]

Allah knows best.