"The delivery is slow."
Translation:Το ντελίβερι είναι αργό.
ντελίβερι is used as a direct translation of the Eng. but only in the sense of "pizza" etc. I doubt that it would ever be used for other kinds: παράδοση εμπορεύματος, "delivery of merchandise" or as you say: απαγγελία/τρόπος ομιλίας "delivery of a speech". Thanks for the observation and giving us the opportunity to comment on this word.
παράδοση delivery correct but separate from tradition because we use the same word for both meanings the one is to send the merchantice or whatever to a person, company etc in greece food services and staff also have delivery to send the food to far away or busy customers all over the place, the other is the tradition customs, folklore, myths and legends of a place :D