Build Signal from open source code and modify some features of original app

Please read and understand what features we want you to add in this app that already the source code is available. We want to use the source code of Signal app to make a new app. The new message app will work with subscription and not free. We will have our server and not use signal servers The new app will have different logo and name. For the server we will use our server with the source code of signal server , modified so he can work with the features we have add in app. The main options you must add in signal cl one app are 1)To work only with subscription .When you download the app either from play store or ios store or from our website , if you want to connect you will need username and password. The username and password will be provided by us with money. Either through play store payments options(in-app purchase) or from our site or ios store. So to connect you have to put the username and password. If the subsciription is expired you cant connect. So no registration with telephone. We dont require other info. You pay and take the credentials for specific time. If user want ,he can put email for reset password option. Connect to our server only with credentials that you buy . You have to create this feature 2. When somebody buy the credentials from us and connect, the first time can create a nickname that other can search to find him and send him message. If the nickname is already taken no-one cant pick it up again (even if the subsciription of the nickname has expired)only if he puts the password that use when he creates at first the nickname (it is the same person he creates it in first place). So you have to create this feature [login to view URL] other options of signal remain exactly the same. End to end etc. Copy the source of signal . Not connect to signal server so cant communicate with other signal users. Communication only with the users of the same app 4)You have to modified the signal server source code to work with above changes. Android and ios apps. Not for pc We want to make a signal alternative with our servers and the subscription will be for paying the expenses of the servers. We want to have longterm relation with the developer so after major signal app updates to update our source code also. The real job is not so much because the source code of signal is available already, you have to modified it to add the features we want.