The soul is the part of us that is there to connect with God. Whether we are three parts (body/soul/spirit), two parts (body/soul), or one part (we are a soul), the soul is what connects with God.

> Parts of the brain dying results in memories or personality changing or being deleted.

This is a tough one to verify since we can't interview the dead. We know that the brain doesn't work the same in some dying people, but are the memories/personality being changed/deleted, or are the pathways merely roadblocked?

> assuming there is a heaven, it shouldn't be there right?

No, this isn't a safe assumption. Even if our bodies get "deleted" (let's say, outrageous explosion, like the Challenger Space Shuttle, for instance), the Bible teaches a restoration/resurrection. There will be a new creation of you.

> So if only the soul exists after death

Therefore this is not correct. 1 Corinthians 15, along with many other Bible texts, go to great pains to assure us that our bodies will exist after death also, just in a different form.

Parts of the brain dying results in memories or personality changing or being deleted. The brain is part if the body so when you die it's gone like any other part of the body and so, assuming there is a heaven, it shouldn't be there right? So if only the soul exists after death, what exactly goes to heaven? It seems like everything that makes you you is in the brain and what's left for the soul?