The stopwatch is only working while it's on the screen and the screen is active. Notifications stay there until you manually discard them. The heart rate sensor is a complete toy since you can only manually trigger it, and it took 2 years for the infinitime devs to read the sensor docs and realise their algorithm is bad. The step counter can only automatically sync, so when it fails to do so for half a day you need to walk around and shake your wrist while keeping you phone and watch screens active. And the list of fails continues beyond that.
On top of that it costs 65€ ($75) when ordering from the European warehouse, and they don't allow you to order from the main one because it would end up cheaper. Don't waste your money unless you need a reason to practice cpp.
Have you updated it this year? 1.13 improved the battery life from 3-5 days to 10+