Note that the microflow does not 'halt' when opening a form, it executes the entire microflow and then the client will be told to open a certain form. So to do what you seem to want to achieve, you should open a form in the microflow, then create a custom 'save' button that is really a microflow and then perform the rest of the steps in that microflow. In this way the changes someone made in the client will have been applied.
OK it works. Thanx!