The article identifies the psychological difficulties faced by adult bilingual students from the post-Soviet countries who came to study at Russian universities, analyzes how these difficulties are related to gaps in the base of their linguistic and cultural linguistic knowledge, and suggests the structure of the educational complex aimed at smoothing the identified problems. In recent years, many Russian universities, working with foreign students, have a new contingent, represented by students from neighboring countries - Ukraine, Moldova, Lithuania, Kazakhstan, Kyrgyzstan, Turkmenistan, Uzbekistan, Tajikistan, etc. Many of them in their countries studied Russian in school and even graduated from Russian schools. At first glance it seems that they speak Russian at the level of native speakers. But the experiment conducted by the authors shows that all bilingual people have knowledge gaps that can complicate communication and lead to misunderstanding. At the same time, their natural-speaking Russian friends and classmates usually do not suspect this and do not take this into account when communicating with well-speaking bilinguals. As a result, such bilinguals often experience psychological discomfort, outsider complex. Therefore, our primary task was to identify a spectrum of difficulties that are common to all bilingual and overcoming of which should form the basis of the special training manual for adult bilingual students. The work has been undertaken in two stages. In the first stage, we conducted a dictation, which showed that 1) the majority of bilingual students make many spelling and punctuation errors; 2) there are some mistakes that only bilingual make (identifying such mistakes allows us to create original training materials aimed at correcting them). In the second stage we tested the level of background knowledge of bilingual students. The test included questions to verify the student's understanding of frequently used 1) idiomatic expressions, proverbs, sayings; 2) stable phrases; 3) standard expressions from books, films, etc.; 4) conversational style patterns; 5) abbreviations, as well as general questions on linguistic and cultural studies. The test results presented in the article in the form of a diagram showed that the maximum number of errors was associated with gaps in knowledge in the use of idiomatic expressions, proverbs, sayings, standard expressions from books and films, as well as stable phrases. The study has not been completed: in the next academic year, the authors plan to conduct another testing of bilinguals in order to identify gaps in knowledge in more narrow specialized areas of Russian culture (Russian music, Russian cinema, classical and modern literature, etc.). However, analysis of the results has already helped to understand what materials should be included in the textbook for bilingual students. In our opinion, this textbook should be a complex that includes 1) a spelling and punctuation course with an emphasis on standard errors that are specific to bilingual students and 2) a manual on Russian culture and its reflection in language. To minimize the large amount of information that should be included in the manual on Russian culture and its reflection in language is supposed to use a digest method involving mobile information from the Internet.