Abstract
Language interference is a key challenge in foreign language acquisition. When learning a second language, students transfer the knowledge from their mother tongue. This article focuses on transfer and interference phenomena between two closely related Slavic languages: Czech and Russian, in the context of teaching Czech as a second language. In particular, the grammatical patterns comprising the copula verb (present indicative) and the auxiliary verb (the compound past indicative) are examined. The study analyzes frequent errors collected from 15 Russian-speaking students from Kazakhstan during classroom interaction in May-June 2025. Furthermore, a marginal analysis on verbs of preference (mít rád, rád) is performed. The findings are used to formulate proposals for teaching methodology.