When you say "default navigation", do you mean the menu that appears in a box on the left hand side? It sounds like you've change a lot of things and now can't find your way back.
To bring the menu back go to the admin page tiki-admin_modules.php and in the Assign New Module section, choose mnu_application_menu in the drop down box. You can assign it to the left or right, doesn't really matter. Make sure the order number is appropriate (check below to see the order of existing modules), and then click the assign button.
As for the wee dotted arrows, I'm not really sure, sounds like maybe you've changed your theme. You could try setting your theme to default2 or tikineat (under the look and feel admin section). Somebody else might have a better grasp of what you've done and how to get things back to the way they were.