There is much mystery and conjecture surrounding what occurs in the very moments of our death, and what happens to our soul, in a technical sense. We simply do not know. It is a mystery. But what we Orthodox Christians do know for certain, is that after we die, we will be raised up again from the dead. We await the resurrection of the dead. This is the fundamental teaching of Christianity. Quite literally, every single person who ever lived will be brought back to life.
And we look forward to the life of the kingdom to come. We also believe the entire cosmos will be renewed and restored. Everything will be made anew. We will be raised into transfigured bodies in a transfigured world. We believe we will then live eternally in the new cosmos, with God and all of restored creation. We will be fully in God’s presence for eternity.
How we react to the fullness of God’s presence depends on the condition of our heart. We will either see God clearly and rejoice (heaven), or otherwise our eyes will hurt with the sudden vision of light after being in the dark so long (hell). Heaven and hell in the Orthodox view are not places as such, rather, they are experiences or reactions to God's full presence in the new cosmos. Reactions to being face to face with pure brightness, innocence and Love.