Many people like to read adventure books or detective stories. A crime is a violation of certain laws and rules. Every natural language is based on a system of grammatical rules - some words or phrases comply with these rules, and some violate them. In this book we present the Polish language step by step in such a way that the reader, like a detective, can independently reveal the grammatical rules on which the Polish language is built, which govern its behavior, functioning, and identify the “criminals”, that is, the existing There are significant deviations from these rules, exceptions that need to be paid special attention to, but which, fortunately, are quite few... This textbook is intended primarily for teaching language at levels from A.O to B.1, although grammatical problems, presented in it go far beyond the boundaries of level B.1. We tried to take into account everything that is essential for the communication process or may be of interest to an inquisitive student who does not want to be limited only to the initial stage of learning.