You would have simply said that you are not aware of Arsenal's interest in Osimhen. A quick Google search would have help you to see that the news received headlines in some news outlets.
Again, there was no real interest from Arsenal for Osimhen. There's a difference between keeping tabs on a player and being interested in the player. Just like Viktor Gyökeres, the Sporting CP striker, a lot of big clubs are keeping tabs on him, but no club has shown any real interest. A Google search like you say might show that Arsenal are interested, but they've not done anything to indicate that.
Regarding the striker's disagreement with coaches, he had one with former French Napoli coach Rudi Garcia. The Nigerian reacted angrily at the coach when he was substituted.
Oh, I remember that incident. Is that what you call a disagreement? I can swear that players do that almost every week. They get upset when substituted and even kick water bottles and water coolers, some ignore their coach and teammates. These things are normal "heat of the moment" behaviour, which I don't encourage of course, but you can't call that a disagreement when so many players are guilty of that in their careers.
I agree that Osimhen has anger issues, but like I said earlier it is taken out of proportion.