First, as this is a concerto, consider for yourself which sections feature a large ensemble and which feature a small one. Some scores may indicate "solo" for the solo instrument parts, which you can use as a reference.

At the beginning, this must be played with a strict, dotted rhythm, full of dignity, like a French Overture. It is by no means a section to be played beautifully or expressively. Consider the music up to the first beat of measure 4 as Tutti.

From measure 5, solo and tutti sections alternate. If your score does not indicate this, please find a score that does. Play the solo sections p (piano) and the tutti sections forte.

For this type of piece, the key is not to beautifully shape the melodic lines, but rather to clearly differentiate the dynamics of each section. As a result, sections may remain flat, either forte or piano, but it is crucial to make the clear distinction between solo and tutti audible to any listener.

Regarding tempo, for example, in measures 41-44, choose a speed at which the whole-note octaves in the bass and tenor continue to be clearly audible throughout.

The key is D major, so play with dignity yet with a sense of joy.