As soon as you've opened a specific type, use Navigate > Go to File Member for a quick overview of and navigation to members in this file.
Alternatively, you can open the File Structure tool window (Windows > File Structure, or Ctrl+F11) for a static display of members in the current file.
File Structure provides additional file browsing capabilities: for example, if you set Automatically scroll to source in File Structure toolbar, every time you select a member in File Structure, the code view area scrolls to the declaration of this member.
The Track caret in editor option works the opposite way: as you move the caret within the code view area, the corresponding member is highlighted in File Structure.
You can learn more about File Structure options in ReSharper web help.
Navigating to a Code File