Key legal question
Whether the seller had given a binding assurance that the property had elevated sound insulation / very good construction quality.
Extracted holding
The statements in the sales materials and purchase agreement were to be understood, in context, as a binding assurance of heightened sound insulation and compliance with the generally accepted rules of building practice.
Extracted reasoning
The advertising text alone was promotional, but the later purchase agreement concretized the contractual content. Under the trust principle, buyers could understand 'very good building standard' as a concrete, objectively verifiable quality assurance.