Grief lasts as long as it lasts. There is no definitive answer because each person is different. It could take months, a few years or even longer. Someone very special to you has gone and that reality will always remain with you, and it hurts. The loss will always be part of your life but the intense pain will gradually subside.
Grief can come in waves and can be unexpected. It can be triggered by little things like hearing a song, seeing a photo, or smelling a fragrance that reminds you of that person, so remember to give yourself permission for this to happen.
Gradually these waves of grief will grow further and further apart. Eventually you will be able to laugh again and remember the life of, and good times with your loved one rather than just their death.