Not all fields of node are present in content
The {{ content }} variable within node templates contains all fields configured to be visible within your content type's display settings. If you experience fields missing, they are most likely disabled within your display.

Head over to your administrative backend's Structure &gt; Content types &gt; [Your content type] &gt; Manage display settings and ensure all fields you are trying to access are enabled for your current display mode.

You can always access disabled fields within your node templates by accessing the original node entity. The node entity along with its fields and some limited accessor methods are available within the {{ node }} variable of your templates.

Use e.g. {{ dump(node|keys) }} for debugging the available properties of the node within your template.

Comprehensive documentation about the variables within node templates can be found within it's header's comment block.