In this presentation, I report part of the results obtained through the survey carried out at four different moments in every five years between 2000 and 2015. After briefly introducing Turkish community in Berlin, as well as linguistic studies on bilingualism of Turkish and some European languages, the outline of my questionnaire survey is presented. Among the collected data, responses from the students of a school in Kreuzberg are used in this presentation to illustrate changes between 2000 and 2015 in their pattern of language use (In what situation do they prefer to use Turkish/German?) and their attitude to language mixing (Is mixing Turkish and German normal/acceptable/wrong?). Based on the responses, I try to show that the pattern of language use remains almost the same, while their attitude to language mixing varies to some extent. The presentation will be followed by an open and casual discussion with questions, comments and criticisms from the audience.