The Reds kicked off their warm-up schedule ahead of 2023-24 against the 2. Bundesliga outfit, with Jota's added-time double the difference at BBBank Wildpark.
Strikes from Darwin Nunez and Cody Gakpo earlier in the game meant it was level entering the latter stages, and Jota delivered two composed finishes to clinch a 4-2 result.
"This was our first game of the season. It's about getting full fitness, giving our best in the moments, pressing, and trying to get some ideas on the ball," the No.20 told Liverpoolfc.com post-match.
"Goals obviously help, the team feels more confident, the players that score, like me, even more. That's what pre-season is all about, [it's] building that confidence and building that fitness into the season."
Jürgen Klopp deployed two different XIs in each half for the meeting with Karlsruher, including 45 minutes apiece for summer signings Alexis Mac Allister and Dominik Szoboszlai.
It was the former's through ball that teed up Jota to tuck home his second goal of the contest - "I start to see I can link up very well with him," said the scorer - and the Portugal international echoed the manager's post-match assessment of positive signs to take away overall.
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Jota added: "I think the last 10 games of last season, when we also played with this system, we showed a lot of signs of improvement, and we now have pre-season to really build on that and these ideas. I think we will be ready for the start.
"Like I said, when you do the things and you are rewarded with the goal it feels better, you feel more confident and it gives you the trust to keep on going."