Bear in mind that it's a recorder sonata, so Telemann was not expecting the player to be able to do much in the way of dynamics. Generally speaking rising passages suggest an increase in tension/excitement, and falling passages an increase in relaxation. Look for the important notes in each phrase and aim for them in your playing. Think about how you want each phrase to sound before you play it.
Articulation should be generally legato (tongued rather than slurred, unless slurs are marked) in the slow movement. In the Presto the quavers, especially when moving in step, should be legato tongued, and crotchets lightly detached. Arpeggio-type sections should be played more detached than scale-like sections.
These are generalisations. Feel free to do your own thing with the dynamics and articulation, because what feels right to you will be more convincing than following instructions that feel wrong.
And above all, enjoy the piece.