Use Feedback to Improve a Model

I have developed a ML model for a classification (0/1) NLP task and deployed it in production environment. The prediction of the model is displayed to users, and the users have the option to give a feedback (if the prediction was right/wrong).

How can I continuously incorporate this feedback in my model ? From a UX stand point you dont want a user to correct/teach the system more than twice/thrice for a specific input, system shld learn fast i.e. so the feedback shld be incorporated “fast”. (Google priority inbox does this in a seamless way)

How does one build this “feedback loop” using which my system can improve ?

How can retain the last layer of my model, keeping the weights of all other layers intact?