The Tottenham head coach watched his side put recent domestic frustrations to one side with another authoritative European performance, following last week's impressive win over Borussia Dortmund.
Second-half goals from Randal Kolo Muani and Dominic Solanke settled the contest in Germany and lifted Spurs to fourth place in the league phase on 17 points.
That position secured automatic qualification for the knockout stage and home advantage in the second leg of the last-16 tie in March. Tottenham will face one of Club Brugge, Galatasaray, Juventus or Atletico Madrid.
"We need to take it one step at a time, but to finish in the top eight is a big achievement," Frank said. "To finish fourth in the Champions League is incredible. There are so many positives to take."
"I'm very happy with the result, but even more pleased with the performance. We controlled the game for most of the night. It was a more than deserved 2-0 win away from home."
Frank also praised his players' mentality, revealing Spurs had limited options once again. "We basically had only 12 outfield players available," he added. "A lot of players had to push through the full 90 minutes. The character and mentality in this group is very strong."
Tottenham again lined up in a 3-4-3 system, with Joao Palhinha dropping into the back three in the absence of Micky van de Ven. Kolo Muani led the line against his former club, while Xavi Simons and Wilson Odobert impressed in advanced midfield roles.
Despite their European success, Spurs remain 14th in the Premier League, with just two wins from their last 14 league matches. Frank insists consistency is now the key.
"We've changed the system recently and it will only get better," he said. "The performances have improved. Now we need to turn that into more wins."
Arne Slot has urged Liverpool to cut out mistakes as they prepare for a decisive Premier League clash with Newcastle United, with the Reds boss admitting the race for the top four has reached a critical stage.
Leon Goretzka has confirmed he will leave Bayern Munich at the end of the season after the club and player agreed not to extend his contract beyond June 30, 2026.
Mikel Arteta has called on his Arsenal players to stay calm and confident as they prepare for a tricky Premier League trip to Leeds United, insisting the title race will not be defined by a short dip in results.
Reece James has said Chelsea's dramatic win away to Napoli showed how far the team have come under head coach Liam Rosenior, describing the performance as a clear statement of their growing confidence and belief.
