Not every football player can get this opportunity at the time they want, so the right thing for Osimhen's career would be to go to Saudi Arabia, as you said, with the crazy salary he will receive, he will be able to retire at a very early age if he manages the salaries he earns wisely.
No football player at this age can turn down such a big wage and the right thing for Osimhen is to accept this offer and enjoy the salary he receives. There is a way to get this money at the age of 35 and there is a way to get it at Osimhen's age. 850k per week does not leave any question marks in your mind and opens a clean slate in your mind.