How long do you stay in purgatory?

Christian view:

for all eternity if you believe in Jesus Christ

Muslims view:

The second life after death and after the Day of Hudgement is eternal life. If you worshiped God as the one and only one God with no partner, no son, no companion, no associate, and no equivalence, then you will be accepted by God mercy in the Heaven (God paradise) where you live for eternity.