Trump should end US involvement in Afghanistan and Iraq.
Everyone thought Obama would end these wars, they even gave him the Nobel Peace  prize in anticipation of expected actions but all he did was continue and escalate the wars for 8 years and spend more money than any president in US history.
North Korea is no threat to the US, they're not dumb enough to start a war they know they can't win. Talking and acting crazy is part of their strategy to prevent their greatest fear, US invasion and South Korean takeover.