The Central Office sorts the mail and sends your application to the legal division whose job it is to deal with it, that is, the legal division responsible for the State against which the application is lodged. An application against Germany, for example, will be sent to the legal division that deals with German cases, because the people working in that division speak German and are familiar with the country’s legislation. Your case will then be given a number and examined by a lawyer. This does not necessarily mean that the Court has accepted your application; it just means that it has been registered. If the Court contacts you, you must reply within the specified time, otherwise your file may simply be rejected or destroyed. Once the Court has all the information it needs to examine your case, your application will be allocated to one of the Court’s judicial formations. Throughout the proceedings, even if they seem to be taking a long time, you must wait for the Court to contact you. Because of the large number of applications it receives every year (over 50,000) and the even larger number of cases pending before it, the Court cannot acknowledge receipt of the letters and documents it receives or tell you approximately when your case will be examined. The proceedings before the Court are in writing. Any information you wish to bring to the Court’s attention must be communicated in writing.
https://www.echr.coe.int/Pages/home.aspx?p=applicants/application