If you are watching TENET for the first time, I don't think you can grasp it's content, unless you are a veteran in the field of Physics.
The movie's main content in the reversed flow of time, not the usual 'time-travel'. This conflicts with our regular view of the forward flow. So for those who hate Physics I suggest you should not watch it. Because for you the film would appear a chaos.
All you need is some basic knowledge on entropy-and-other-stuff and some logic to understand the movie. Don't dwell deeper into those concepts while watching the movie. It won't help. Consider reading some movie-explanation if you didn't get it.
For me, TENET is yet another mind-blowing SciFi movie by Christopher Nolan.