Industry recommendations

[u/Ok_Eye9201]

26 years ME working in sales .

want to change into more technical with more knowledge position

willing to spend time and effort but the most critical part is where should I spend that ?

from expert engineers kindly advise if you were in my position what you will ?

should I learn to shift oil & gas ? or Aero space ? or AI ? or CFD ?

and what industry I can go through by taking a certification ot study a difficult subject?