Shower Head Arm Not Straight. the good news is that for most homes, there is a straightforward answer: all brass straight shower arm with flange for fixed shower head ceiling mount.
Jjbex (il) remove the shower head and stick an arm of a pair of channellocks into the showerarm. You might be best to just by a new one, however, one thing you could try is some plumbing tape (ptfe tape, or teflon tape). this extension is available in two lengths — 6 and 12 inches.
Moen S110BN Arris 14Inch Rainshower Straight Shower Arm and Flange
How to replace a shower arm. reinstall the showerhead, tightening it until it is just snug. the old showerhead had an escutcheon plate, the new showerhead doesn't. Now you should have leverage to spin it.