I'd be very surprised if the German law (if actually policed) expands to anything an individual might be insulted by, especially if the offense is one of self image.
You must make intentionally untrue statements with the intent to harm that causes harm.
The truth is a perfect defense. Even if you thought you were lying, you are protected. If you believe what you are saying, you are protected. If you did not know for certain that you said a lie, you are protected. If you did not mean to cause harm, you are protected. If no harm occurred, even if you tried to cause harm, you are protected.
The standard is extremely hard to reach, possibly even too hard, and it is clearly qualitatively different than most other countries.
> The truth is a perfect defense. Even if you thought you were lying, you are protected. If you believe what you are saying, you are protected.
IIUC the truth is a perfect defense in most states, but in some states maliciously stated truths (insults, more or less) can be defamatory. For example, see Johnson v Johnson in Rhode Island, where one Clifford Johnson was required to pay compensatory damages for (more or less accurately) calling his ex-wife a "[redacted] whore" in public. (He was also initially ordered to pay punitive damages, but that was reversed on appeal.)
> If you did not know for certain that you said a lie, you are protected.
I don't think this is the case in most states. If you say something with reckless disregard for the truth, it can be defamatory.
> If you did not mean to cause harm, you are protected.
I think this is typically only true of defaming public figures.
And these kinds of laws also exist in more extreme "free-speech" countries like the United States (where the guarantee of free speech doesn't cover, for example, libel).