Terzic refused to comment on reports that Dortmund were set to sign Werder Bremen and Germany striker Niclas Fullkrug (30), saying his focus was solely on the game and giving Dortmund fans something to smile about on Friday.
Last season's runners-up, who missed out on the Bundesliga title after dramatically slipping up on the final matchday, narrowly won their season opener against Cologne courtesy of an 88th-minute winner by Donyell Malen.
They followed that with a drab performance and a 1-1 draw at Bochum, with their attack looking toothless for much of the game.
"We know that our appearance in the last two matches was not what we wanted. We want to improve markedly and win the game," Terzic told a press conference. "We have not yet managed to send our fans home happy."
"I am sure we will show a different face tomorrow and win at home. The lads know what to expect from Heidenheim tomorrow.
"They also knew it last week against Bochum but we still struggled, especially in the first half, and this should not happen again. I am confident we are on the right track."
With last season's Bundesliga top scorer Fullkrug reportedly in Dortmund on Thursday for a medical, Terzic said: "As far as I know he is a player of Werder Bremen so I don't want to talk about it. He is not here."
Bayern Munich also face a testing encounter, travelling to Borussia Monchengladbach, a team they have failed to beat in their last five matches across all competitions.
Since the 2011/12 season no other team has won more matches against Bayern in the league, with Gladbach boasting 10 victories, with nine defeats along with five draws.
The Bavarians are confident they have what it takes to end Gladbach's unbeaten streak, with record transfer Harry Kane having already scored three times in his two league games since joining for 100 million euros from Tottenham Hotspur two weeks ago.
The Bavarians have enjoyed a solid league start with two wins from two matches. Union Berlin will also be looking to make it three wins from three when they host RB Leipzig on Sunday.
