When the player is under contract with the club, then even if the player does not want to leave but the club wants to sell him, then it will definitely happen transfer. now I also see Arnold is one of the important players for Liverpool and honestly I also see Liverpool will consider with long consideration if then they think of selling him. For now the possibility of him staying at Liverpool is still very large, but when the offer comes and the amount is tempting, then it also does not rule out the possibility of changing their decision in the end, either from the side of the player or the club.
When you’ve awakened to the point that football could be considered more of a business than a sport for entertainment, then you won’t be so surprised by clubs letting go of top players that is still relevant and could still perform well in the squad for the right price.
Admittedly, that money would probably be used to bolster whatever position seen to be underperforming in the squad.