I managed to successfully update from Magento version 2.02 to 2.04 using the System Update tool within the admin panel. However, since then both my website and admin appear broken. It seems all formatting is lost and content appears as lists of text.
maybe it could be permissions or owner misconfiguration after upgrade.
This is a very common case when upgrading Magento to the newest version. You should migrate all data to another 2.0.4 Magento site with this tool http://tinyurl.com/zeqk3ue . This will not affect anything to your store. It also migrates SEO URLs so you don't need to worry about your SEO rankings.