20/300*5000=333.3 minutes. This is just over 5 hours. You have plenty of time before 14 July.
Other than that, nobody can tell you how to do it right unless you first show us how you have done it wrong.
if your problem is in sketch, use this:
Dim swDoc as ModelDoc2
set swDoc = swApp.ActiveDoc
'InsertSketch then add these 2 line before drawing
' write your code for drawing in sketch then add these 2 line after
' then close your sketch
Good Luck :-)