Yes, Heaven exists. It's right here, if we are open to see it. Christ said that the Kingdom is within you. Most people cannot see it, for they are spiritually blind.
The after-life is different. After-life merely means without a human body. You can be with a human body and still have Heaven. It's called being with the Holy Spirit (your true self). Most people choose Ego, instead of the Holy Spirit. Ego was the original problem which created the separation we suffer. Ego is selfishness.
If we decide to follow Ego rather than Love (God), then that is our choice. One choice leads to "Hell" and one leads to "Heaven." But we don't have to wait for final judgment to achieve Heaven. We can do that now, long before we die.
The judgment is borne out of our own free-will choices. We can help our free-will choice by choosing our friends and associates wisely. If our friends are corrupt, promoting a corrupt lifestyle, then we can choose to leave or stay. Staying will only make it more difficult to find Heaven.
The after-life for most is full of darkness and confusion, because spirit without a human body cannot see so long as they are trapped in Ego (selfishness and separation). If a person vanquishes Ego and resumes the Holy Spirit, then bodily death does not end continuity of consciousness. Thus "everlasting life" is achieved, and "after-life" takes on a new meaning -- life in the spirit and no longer a need for incarnations in order to find the way out and the way back to God.
Each human body has only one life, but the immortal child of God may have many. Final judgment of the immortal spirit has not yet come, though each individual life has already been judged so that a new incarnation can be chosen for them -- one appropriate for their next set of lessons.
Christ said that the "first" (Egotistical) shall be last (left out of Heaven); and that the "last" (humble) shall be first (welcomed into Heaven).
It's simply and only a matter of choice -- whether to be selfish or unconditionally loving.