Trumpelmann's 3-17 helps Namibia restrict Scotland to 109-8
The left-arm quick justified his team's decision to bat first in Abu Dhabi as he struck with the first ball and then got two in successive balls including Richie Berrington for nought.
Berrington, who was standing in as captain with regular skipper Kyle Coetzer out nursing a finger injury, reviewed the call but replays suggested the ball would have hit the leg stump.
The opening over provided a stunning start for a team, ranked a lowly 19, that stormed into the their first ever Super 12s of the tournament after wins over Netherlands and Ireland in the qualifying stage.
Trumpelmann returned his T20 best figures of 3-17 in his sixth international in the shortest format.
David Wiese trapped Craig Wallace lbw for four to rattle Scotland, who lost their Super 12 opener to Afghanistan by 130 runs.
At one stage Wednesday, the Scots were 18-4.
Opener and wicketkeeper-batsman Matthew Cross attempted to stem the rot with Michael Leask but another left-arm fast medium Jan Frylinck bowled him for 19. Cross took 33 balls for the effort.
Leask played a lone hand with his 44 off 27 deliveries before being bowled by JJ Smit.
The bowlers kept up the pressure in the final few overs with Frylinck returning figures of 2-10 from his four overs.
Chris Greaves made 25 and was run out on the final ball of the innings.