As soon as you've opened a specific type, use Navigate > Go to File Member (_Alt+_Backslash) 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+Alt+F) 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.