The new 2020 block-buster from Christopher Nolan is definitely a very 'confusing' film making masterpiece. As an English Literature student from University College London, Christopher Nolan is a master at hiding the genuine meaning of the movie behind all of those complicated scientific knowledge. In fact, Nolan's past films all focused on themes that goes beyond science, for example, Interstella - Love transcends time and space, Batman Triology - Politics, humanites and Inception - Unconsciousness, Dream.
With that being said, why don't look at TENET from another perspective rather than trying to solve all of the complicated scientific knowledges?
So, what is Christopher Nolan actually trying to say? From the fact that when you invert yourself, you are not actually travelling through time. Instead, you are reversing your entropy which means you travel back in time but not forward. This essentially means that you are spending you actual time left in this world to go back to the past. As Niel constantly reminds the protagonist, "Whats happened has happened." No matter what has happened in the past, there isn't a way to go back in time and change anything. By living in the past and desperately seeking a way to change the past, we will only be spending every next precious minute that we have and that we could spend on for a more promising tomorrow.