Here are the tips I use to finish my workshops on time:
Create a workshop schedule with a breakdown of every activity (including introduction, breaks and conclusion) and assign a number of minutes for each activity. To do that you can use the free Workshop planner template
Use a timer to know how much time is left in each activity. You can make that timer visible to all by using an app like Big Timer.
Add the starting time for each activity. For example, next to an activity, I write: "10:15", so that I know that this activity should start at 10:15 if we are on time. This helps double-check quickly during the workshop if we are on time, if we still have some margin of error, or not.
Add a buffer at the end of your workshop (I often use 30 minutes) as a margin of error in case an activity takes longer or you need to improvise another activity on the spot.