By Patrick Austen-Hardy Kai Havertz has revealed that Mikel Arteta’s advice to back himself in the opposition penalty area has worked wonders for his confidence. The German endured a slow start at the Emirates Stadium after his surprising £65million move from Chelsea. Havertz, 24, only scored one goal in his first 12 Premier League games for Arsenal. But he is finishing the season strongly with eight goals and five assists in his last 12 league appearances, includinga brace against his former side. Arteta has repeatedly defended the silky German, who was fiercely criticised in the first few mo…