Harley-Davidson Sportster 883 USA Import indicators act as brake lights.

Moin moin from Hamburg, I’m new here in the forum and I have a question for you. I imported a Harley-Davidson Sportster 883 from the USA. Now I want to rebuild it and bring it to the TÜV. Maybe you can help me with a problem. The two rear turn signals shine with (red turn signals) when I press the brake. According to Tüv this is not in order and needs to be rebuilt. Unfortunately I can’t find a schematic or any other thing on the internet where I can recognize ka nn how the whole thing is switched and what has to change so that the turn signals no longer with brakes. I would be happy if someone could help me. Greetings Marco