Yes, Germans say numbers like that. (It only applies to the tens tho)

Roughly translated you'd say two-and-ninety (without the minus, I just made those so it doesn't look that cursed)

It's mainly because at least in German it flows better than ninety two would. There have been pushes to accept ninety two as well but acceptance has been and continues to be scarce.

Yes, and it's so annoying. I'm Austrian, a bit dyslexic, and sometime I just can't sevenandeighty sixandseventy.

some (very few, i think it's only the "teens") english numbers are like that, like seventeen (7+10) for example

Afaik, they've changed the official system from the "German" to the "Swedish" order after WW2, but it is still used by many in spoken language.

Old people tend to say 2+90 while young people say 90+2. I heard that this new way of saying it was due to the introduction of the telephone, where people needed a more linear way of saying the numbers to reduce confusion. But I don't have a source.