This study explores the impact of a bilingual PrimarWebQuest on the mathematical and linguistic learning of primary school students in Germany. The research focuses on how bilingual education can enhance students' understanding of mathematical concepts, particularly in the context of measuring length. The study investigates the contribution of bilingual PrimarWebQuests to both subject-related and linguistic learning, as well as the intercultural aspects of using the US standard system alongside the metric system. The measurement of length is a familiar concept for students and serves as a foundation for understanding numbers and other measurement systems. In bilingual classes, introducing the US standard system offers opportunities for intercultural learning. Students can compare the two systems, deepening their understanding of the metric system's decimal structure. Bilingual education in Germany involves teaching subjects in a different language for a fixed time. In bilingual mathematics classes, linguistic negotiation processes help develop precise mathematical concepts. The study uses PrimarWebQuests, an inquiry-based method, to facilitate dialogues and deepen students' understanding of mathematical terms. The research was conducted with two groups of fourth-grade students in a bilingual school in Germany. Mathematics is taught in English or German, depending on the topic. The PrimarWebQuest aimed to familiarize students with the US standard system and develop their ability to convert between the two systems. Authentic materials were used to help students develop ideas about the new units of length. Data from video recordings were analyzed using interaction analysis to reconstruct how students create and negotiate shared meanings. The study aims to provide preliminary results on the effectiveness of bilingual PrimarWebQuests in enhancing mathematical and linguistic learning.This study explores the impact of a bilingual PrimarWebQuest on the mathematical and linguistic learning of primary school students in Germany. The research focuses on how bilingual education can enhance students' understanding of mathematical concepts, particularly in the context of measuring length. The study investigates the contribution of bilingual PrimarWebQuests to both subject-related and linguistic learning, as well as the intercultural aspects of using the US standard system alongside the metric system. The measurement of length is a familiar concept for students and serves as a foundation for understanding numbers and other measurement systems. In bilingual classes, introducing the US standard system offers opportunities for intercultural learning. Students can compare the two systems, deepening their understanding of the metric system's decimal structure. Bilingual education in Germany involves teaching subjects in a different language for a fixed time. In bilingual mathematics classes, linguistic negotiation processes help develop precise mathematical concepts. The study uses PrimarWebQuests, an inquiry-based method, to facilitate dialogues and deepen students' understanding of mathematical terms. The research was conducted with two groups of fourth-grade students in a bilingual school in Germany. Mathematics is taught in English or German, depending on the topic. The PrimarWebQuest aimed to familiarize students with the US standard system and develop their ability to convert between the two systems. Authentic materials were used to help students develop ideas about the new units of length. Data from video recordings were analyzed using interaction analysis to reconstruct how students create and negotiate shared meanings. The study aims to provide preliminary results on the effectiveness of bilingual PrimarWebQuests in enhancing mathematical and linguistic learning.