Purification through punishment in hell
Sinners among Muslims will be punished first in hell and we don't know the duration of that punishment (number of years or centuries etc). After purification through punishment, they will enter paradise except those Muslims who committed Shirk (openly or secretly). Some striving Muslims who are steadfast in committing towards major obligations of Islam, have love for Prophet (pbuh) and repenting for their sins could be pardoned and ALLAH knows best. May Almighty Allah include us among His righteous slaves - Aameen.