The core activity of Frunz AG encompasses three main areas:
1. **Construction**: The company offers services in the field of civil engineering and construction.
2. **Real Estate**: Frunz AG is also active in the real estate sector, although the specific activities in this area are not precisely defined.
3. **Hazardous Substance Remediation**: A significant part of the company's activities involves the remediation of hazardous substances, including consulting, sampling, building analysis, remediation concepts, professional execution, measurements, and disposal of hazardous materials, such as asbestos.
Overall, the core activity of the company can be described as comprehensive services in the areas of construction, real estate, and environmental remediation.