If your homepage is broken and your property pages return 500 errors after updating to YOOtheme 5, a third-party builder plugin is the likely cause.
Why this happens. YOOtheme 5 changed its builder element API significantly. Custom third-party builder elements built for YOOtheme 4, such as Flart Studio’s fs-grid, fs-modal, and similar plugins, break under this change.
What you can do. Update those third-party builder plugins to their current YOOtheme 5-compatible releases, available from the plugin vendor’s account portal. If updated versions are not yet available, the fallback is to roll back to the previous YOOtheme version using a backup taken before the upgrade.