As mentioned here, the integration course certificate can facilitate the processing of your file by the authorities and therefore improve your chances. However, it's not compulsory: "You can furnish proof of an adequate command of the German language as well as of your basic knowledge of the legal and social system, but also other things when appearing in person.", as per stated by the Foreigner's office. So while a language course certificate is something you can't not provide, the rest will be assessed during your interview.