How much do I have to exercise for it to make a difference?

Insulin sensitivity is improved/increased for up to 24 to 48 hours after exercise. Ideally you should not go more than 2 days in a row without exercise. If you exercise consistently you will like see more improvements in blood glucose levels.

It is suggested that you exercise around 150 minutes per week, spread out during at least 3 days per week, with no more than 2 off-days in a row. There are many types of exercise to choose from! While this is the recommendation, it is still beneficial to exercise even if it is not at this amount! Here is some more information that may be useful: https://type2diabetes.com/fitness-and-exercise