Here you can find the instructions on how to enable the Flat Catalog.
- Switch to you Magento Dashboard.
- Go to the Stores > Settings > Configurations section.
- Expand the Catalog tab the left panel, and tap Catalog.
- Skip to the Storefront section.
- Set Use Flat Catalog Category and Use Flat Catalog Product to “Yes”.
- Press the Save config button.
- ✓ Refresh the Magento cache.
