1. An apparatus for performing a plurality of operation steps of a dialysis process, said apparatus comprising: a process controller for controlling the apparatus to perform the operation steps of the dialysis process, monitor process progress of the dialysis process and monitor sensor inputs of sensors of the apparatus; and a user interface comprising a display, an input device and a user interface controller, wherein the user interface controller is connected to enable presentation of graphical data on the display, and wherein the user interface controller is connected to enable user interaction with the graphical data and connected to exchange information with the process controller, wherein the exchanged information is based on the user interaction of the user interface and monitoring of process progress of the dialysis process and sensor inputs of sensors of the apparatus monitored by the process controller, and wherein each of the operation steps are classified in the user interface controller as one of a sequential operation step, which is dependent on completion of another operation step, and a non-sequential operation step, which is independent of completion of another operation step, the user interface controller is configured to represent each of the operation steps by an operation step item which is a graphical item suitable to be presented on said display, and the user interface controller is further configured to dynamically, for each of the operation steps, control enabling and disabling of selection among the corresponding operation step items based on a state of the respective operation step, wherein a completed state is assigned to each operation step that is completed, a non-completed state is assigned to each operation step that is non-completed, a selectable state is assigned to each operation step item of an operation step that is non-sequential and each operation step item of an operation step that is sequential but only in relation to a completed operation step, and a non-selectable state is assigned to each operation step item of an operation step that is sequential in relation to a non-completed operation step.