About
Twenty years, one habit: understand the system before changing it.
I studied computer science at TU Berlin, then moved to the Universität der Künste for a Diplom in electronic business. Engineering on one side, design on the other. That still describes how I work: I can read an API spec and argue about a flow in Figma in the same afternoon.
My first product job was at Jamba! in 2005, launching mobile web in more than 20 countries and adding €40M in turnover. A/B testing there lifted conversion 48%, and I haven’t stopped testing since.
In 2009 I co-founded M47 Interactive, a bootstrapped mobile startup where I was product and tech lead. Without outside money, our dating app grew to a million users and a #1 Google ranking. In parallel I was running two solar import companies, which is further down this page.
Since then I’ve mostly worked as an interim and contract product lead. Companies bring me in when the problem is urgent and tangled: a backend migration under live traffic at Douglas, a regulated investment platform at WIWIN, a charity lottery shop at Lotto24 that had to launch on a tight timeline. Today I’m Principal Product Owner at Sonova, working on a platform that routes consumer demand for hearing care to independent partner stores.
Short projects are the format I’ve chosen, and I do stay when something is worth it. I’ve supplied apps to A1 Telekom Austria since 2013, co-founded RoofUz in 2022, and have co-run Weserland, a Berlin coworking space for 40 creative freelancers, since 2011.
How I work
Four things I do on every engagement.
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Find the real constraint
The blocker is rarely where it looks. With the solar brands it was bank financing, not price. At WIWIN it was trust, not features. I go deep until I can name it.
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Measure the change
A/B tests and usability labs at Jamba!, mobileJobs, WIWIN and ON moved conversion by +48%, +28%, +50% and +7%. If a change can’t be measured, I’m careful about calling it a win.
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Give teams room
I do my best work with people who take ownership, and I try to create the conditions for it. At ON I moved dedicated teams into squads and brought in an agile design process, and features shipped 20% faster.
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Say what you know, and when you’ll know more
I once went quiet during a crisis while I worked out the right answer. It cost me trust. Now stakeholders hear what I’m doing and when they’ll get an answer, even mid-analysis.
What clients say
“Thank you Felix for taking over the interim product management for our mobile-first-site freiheitplus.de delivering the MVP on time! You showed us strong product, tech, communication and agile management skills.”Björn Behrendt, Co-Founder & MD, MarketingPush, on the freiheit+ launch (LinkedIn recommendation)
The energy thread
Solar modules, a utility portal, and a campaign to quit coal.
2008 – 2012: BSL Greentech and Felix Solar. I founded and ran two trade companies importing photovoltaic modules from Chinese manufacturers, by the container, through Rotterdam and Hamburg. We sold direct to installers and EPCs in Germany and Italy, the two biggest European solar markets of the time, and reached roughly €1M in annual revenue across a portfolio of module brands.
The hard part wasn’t selling modules. German banks would only finance installations using brands with a local track record. An unknown brand couldn’t sell at scale, however good or cheap it was. So I set up the reference projects the banks needed and took two brands from unknown to bankable.
When Germany cut its feed-in tariffs in 2011 and 2012, domestic demand dropped sharply. I read that as the signal to wind both companies down, and I did.
2019: climatecampaign.com. A self-started initiative to help people switch to renewable electricity providers.
2020: STADTENERGIE. At interstruct I shipped a mobile-first site and self-service portal for this utility.
Since 2022: RoofUz. A co-founded platform bringing digital processes to wood construction, a trade that has barely been digitized. It won the BIM-Löwen award and was named one of the top 50 European startups.
Full record
Every engagement, with what changed.
| Period | Company and role | What changed |
|---|---|---|
| 2026 – | Sonova · Principal Product Owner | Lead-routing platform connecting consumer demand to independent hearing-care partners |
| 11.2025 – 05.2026 | Trusted Shops · Principal PM, D2C apps and web portal | #1 brand keywords in 10 markets; 4.7 rating through rebrand; +27% sign-ups |
| 09.2024 – 07.2025 | ON · Principal PM, D2C e-commerce app | 20% faster delivery; A/B testing program, +7% conversion; cross-country ASO |
| 03.2024 – 08.2024 | Lotto24 · Principal PM | Launched the freiheit+ charity lottery shop on a tight timeline, hitting CAC targets |
| 05.2022 – 08.2023 | WIWIN · Principal PM | BaFin-compliant investment platform; KYC, payment, tokenization; +50% conversion |
| 2022 – | RoofUz · Co-founder | Digital processes for wood construction; BIM-Löwen award |
| 02.2022 – 04.2022 | IONE Software · Principal PM | POS order module; bill splitting and business-meal flows |
| 05.2021 – 09.2021 | TLGG · Product Owner | D2C food-supplement store concept; basis for a C-level go/no-go |
| 08.2020 – 04.2021 | Douglas · Principal PM, Retail Apps | 4 Scrum teams; zero-downtime SAP Hybris migration; search redesign |
| 03.2020 – 09.2020 | interstruct · Product Manager CX | Mobile-first site and self-service portal for utility STADTENERGIE |
| 02.2019 – 07.2019 | Eurowings Digital · Senior Product Owner | 3 Scrum teams; navigation redesign; taxi, rail and bus partner integration |
| 11.2018 – 03.2019 | mobileJobs · Product Manager | +28% conversion in blue-collar recruiting funnels via A/B testing |
| 04.2018 – 08.2018 | Cornelsen · Product Strategy Manager | C-level digital-learning strategy from market and regulatory analysis |
| 09.2017 – 04.2018 | Lokalleads · Product Owner | B2B automation and sales backend for craft businesses |
| 08.2016 – 08.2017 | IONOS · PM Mobile Messenger | Secure messenger to 250k users within weeks; invented RealEmoji |
| 06.2013 – | A1 Telekom Austria · App supplier | 10+ branded apps across iOS, Android and Windows; budget responsibility |
| 01.2009 – 03.2015 | M47 Interactive · Co-founder | Bootstrapped dating app to 1M users; performance-based ad system |
| 2008 – 2012 | BSL Greentech, Felix Solar · Founder | PV import into Germany and Italy; ~€1M revenue; two brands made bankable |
| 10.2005 – 08.2008 | Jamba! · Product Manager Mobile | Mobile web in 20+ countries, +€40M turnover; +48% conversion |
Education and languages
Trained in both code and design.
Universität der Künste Berlin, 2001 – 2005
Diplom (Master’s), Electronic Business
Technische Universität Berlin, 1999 – 2001
Vordiplom (Bachelor’s), Computer Science
Languages
German, native. English, C1, the working language of every product team I’ve been part of for the last decade.