I think both Newcastle and Liverpool played very well, Liverpool managed to comeback during injury time, while Newcastle can manage to equalize the scores even though they're only playing with 10 players.
Rather than trying to sign Isak, it's better for Liverpool to pay attention with their defending line, I think they have to sign more defenders.
To be honest, no one could have predicted that Newcastle would score two goals when they got down to ten men. I was surprised when Guimarães gave them an equalizer in the 57th minute, because this was the same team that failed to beat Aston Villa in the first game of the season when playing with ten men. Even though they lost yesterday, Newcastle still surprised us. I agree with you that Liverpool should improve their weak defensive and not worry about signing Isak because they already have good attackers.
Ngumoha is just sixteen, he has a good mentality since he's not afraid to play in St James Park.
However, I started watching Ngumoha during their preseason games, the young player has been doing well since the friendly match, and I believe the boy deserves to be given some chances in the Premier League since he has something to offer. The 16 year old scored four minutes after subbed in to put Liverpool back on their way, I hope Arne Slot gives him more minutes in the next games.