Yes, every network call has to asynchronous. You don't need to make every single method in you class async, but i would refactor the code in a way that only one peace of code actually does the calls and this peace has to be async. If you have following code that depends on the response from the server, then use a callback.
In pseudo code that would look something like this:
void makeNetworkCall(command, listener){
async(){
result = command.execute();
listener.onCommandSuccess(result);
}
}