Ideally, if I were his advisor back in 2016-2017, I would have advised him to do the following:
1) Go on to Twitter, and pronounce: "Now that I am President of the United States, I will adopt a demeanor that acknowledges the gravity of the office, and affords it the respect it deserves."
2) Assign three people to serve as your attack dogs: Donald Trump JR, Steve Bannon, and Mark Meadows. You, President Trump, will still be writing those tweets, but they will deliver them.