Wie sagt man das auf Deutsch? “What are you taking about this is unbelievable “

Please explain each word in sentence if possible

Sehen Sie eine Übersetzung

What are you t a l k i n g about?

Worüber sprecht ihr (sprichst du/sprechen Sie)? Das ist unglaublich.

The second part can be literally translated:

Das ist unglaublich.
This is unbelievable.

As to the first part:

What about? These words are in German normally combined into a pronominal adverb:
Worüber?
You can be "du" as an informal adress to one person, as informal adress to more than one person it is "ihr" and as formal adress to one ore more persons it is "Sie".
are talking - there is no progressive aspect in German. So you just use simple present/Präsenz "sprechen", the correct form (sprichst/sprecht/sprechen) depends on the meaning of "you" (see above). If the progressive aspect is of importance you can express it by an adverb "gerade" ("sprichst gerade", "sprecht gerade", "sprechen gerade").

So it is in German:
Worüber sprichst du (gerade)?
or: Worüber sprecht ihr (gerade)?
or: Worüber sprechen Sie (gerade)?

Colloquially you find also the expression "über was?" for "what about". So that is literally the same as in English. But the word order is different: Über was sprecht ihr (gerade)? usw.