When I use wordpress on PC, I can simply press ctrl+1 for Heading1 and ctrl+2 for heading 2... But when I use my mac it doesn't work. What are the shortcuts for heading styles on safari?
Short answer- there aren't any.
If you click the help button in the editor, then the hotkeys tab, you'll see the available shortcuts for the current OS/Browser. In OS X the modifier is Command instead of Control, but there aren't any shortcuts for headings.