Trouble friends who know CAD or mechanical parts to see how the arc should be drawn on this drawing?

In the first figure: the arc you are talking about is not a circular arc but a smooth curve at one end - a coherent line, its curve can be drawn through the three-dimensional drawing, this smooth curve is no center of the circle, or the center of the circle is a formula curve;

In the second figure: the diameter of the 16th is a round hole, if it is a threaded hole there is no angle provision you are talking about;

Also, there is one thing you should note in the mechanical drawing standard dotted line

Another thing you should note is that dotted lines are not allowed to be dimensioned in mechanical drawing standards.

I hope this helps.