There is hardly any written phrasing in Bach's keyboard music.. One way to get an idea - is to look to his writing for violin..where much can be gleaned on his thinking w re to his articulation…
Much of the time, the phrasing goes over the bar line.. One can also read Kirkpatrick's writings on this.. Or listen to his vocal phrasing in cantatas etc.
Have you asked your teacher to explain How to understand his articulation?
Or perhaps, you are just meaning ornamentation… for that, there is a legend, usually printed at the beginning/end of some editions for clavier… (not hard to find.