On the company's website, under "Projekte," there are pictures labeled as files with the names of the clients. This is not a "perfect score" yet, but it is typical of a company whose satisfied customers are real and should not be hard to find on site. I did not find a construction service description there – based on my experience with assessing construction companies "according to the website files," I consider the company worth being shortlisted. Apparently, they use building materials from regional manufacturers and work with local craftsmen. The company brochure also boasts "only a single contact person" throughout the entire project. I guarantee nothing, but my conclusion is that further discussions are likely worthwhile.