[TYPO3-install] Update of typo3 via Bitnami

[iam li]

Hi Typo3 users, I have a simple question to which i wasnt able to find an answer. Basically, when you have typo3 already installed but want to update to a newer version, will the installation with Bitnami overwrite over everything we have or will it make the update and everything will be preserved? (updating from 7.5.0 to 7.6.8)
what would be the procedure?
thanks !