Servus: Viennese way of saying “hello” like the Italians say “ciao” or the French say “salue”.
Say again: Short from to say: I am sorry I did not hear and/or understand what you just have said, would you please repeat if you don’t mind.
ETD (estimated time of departure): after serious considerations and to my best current knowledge I would like to inform you that this might be the time of (my) departure.
ETA (estimated time of arrival): after serious considerations and to my best current knowledge I would like to inform you that this might be the time of (my) arrival.
Go ahead: Please be so kind an proceed with what you have just started or suggested to do.
WilCo (will comply): I will do all the needed to achieve exactly what you have asked me to do.
Affirm: I do agree or confirm exactly what you have told or written to me.
Negative: What ever you have just said I don’t agree with and/or don’t like or I don’t think that you are right about what you just have said.
ML (Markus Lehner): Mr. Oskar Klein always signed “OK” when he approved a new car leaving the production line, but since I am not Mr. Klein I confirm or agree to certain requests with my own initials.