No, it is only rude to do it in a rude way or to gloat while doing it.
when you bite someone's thongue while kisiing him or her then it is rude
Yes, it is generally considered rude to interrupt someone while they are speaking. It is important to listen and wait for your turn to speak in a conversation.
It's considered rude everywhere, not just Germany.
no this is not rude
yes,it is rude
Yes, they can be a rude words when directing them at someone.
Asking someone for their pronouns is not considered rude; it shows respect for their gender identity.
if they are rude to you
Yes
It usually depends on context, but would you be offended if someone called you 'American' while on England?
Simply say " How RUDE" and walk away. That is what it is RUDE.