Manchester City overcame bitter rivals Manchester United at the Etihad Stadium to get back to winning ways in the Premier League.Phil Foden’s header and a second half Erling Haaland brace helped City on their way to an emphatic victory, despite not even getting out of second gear.United had a few opportunities, largely through Bryan Mbeumo, to pull a goal back in the game but simultaneously, it could’ve been more for the Blues with Haaland and Tijjani Reijnders both missing guilt edge opportunities.With the three points, City have moved up to seventh ahead of a big week, where they host Kevin de Bruyne’s Napoli in the UEFA Champions League on Thursday and title rivals Arsenal at the Emirates Stadium l on Sunday.Here are three things we learned from victory on Derby Day:Individual performances make a huge differencePlenty of the players who didn’t deliver against Brighton and Spurs were magnificent yesterday.Ruben Dias was fantastic, winning aerial and ground duels and passing the ball out from the back well. He was partnered for the first time this season by the ever reliable Josko Gvardiol. Abdukodir Khusanov and Nico O’Reilly at right back and left back respectively also had extremely good games.Phil Foden looks back to his best in midfield. In the first half particularly, he ran the game, and scored a very well deserved goal.Speaking of goals, Erling Haaland is Erling Haaland. He loves the Manchester derby and has started this season like a house on fire.But other than perhaps the big Norwegian, the best player on the pitch was Jeremy Doku.The 23-year-old winger was scintillating, and showed real end product as well as the sharpness in his dribbling with two assists.He’s practically unplayable in the form he was in yesterday. Just when I give up on him and feel like he’s not good enough, he puts in a performance like that. He now must translate this into consistency if he is truly to become one of the best wingers in the league.But for yesterday’s win, he contributed hugely. Him, Dias, Haaland and Foden all playing well turns an average City team into one that can go into any game and expect to win.But City are far from the finished articleThere are issues, however – ways in which City are still miles off where they used to be.Rodri, Bernardo Silva and Reijnders all had under par games. They were all better in the second half than the first, but were also overrun at times and quite sloppy with possession.United broke through the lines too easily. They were very poor in the final third, but a more clinical team would’ve created a few more clear cut chances than Ruben Amorim’s team did.They also relied on a wonder save from new goalkeeper Gianluigi Donnarumma to prevent United from halving the deficit at a time where they’d had a lot of possession and were building momentum.It’s unfair to discredit his save – such an action is exactly what Donnarumma was brought into the club for – but it’s not ideal for City to concede such chances in the first place.The one disadvantage to bringing the Italian into the club is his distribution. It’s clearly a level below Ederson’s, and I personally am not convinced that playing more long balls will be beneficial for City in the long term.But the only way is up; this will be a season of transition for City and Donnarumma, Reijnders and the other new signings will adapt and make an even bigger difference to the side than they have done already I’m sure.Leadership and talismen will carry us throughCity seem to have much more leadership in their ranks this season, which will hugely benefit them in tough moments.At the back, Donnarumma is a calm and reassuring presence. He commands his penalty area extremely well and is a talismanic figure in between the sticks.Him, Dias, Gvardiol, Rodri and Haaland is a spine that matches any other team in Europe – and a fully fit Foden can be added to that.Those six players alone when playing well can carry a team through big games, which is something that I expect them to do on a regular basis this season.