Mikel Arteta says Arsenal “will not sit still” and are “very ambitious” with what they can still do in this summer transfer window.The Premier League champions started their pre-season on Saturday with a 4-1 win over Girona, in which summer signing Christos Tzolis scored his first goal in their colours.The Greek international arrived for €40million from Club Brugge as the first new outfielder in Arteta’s squad. A loan deal for Piero Hincapie had previously been made permanent earlier in the summer and was followed up by the free transfer of former Leeds United goalkeeper Illan Meslier.Arsenal are still in the market for a left winger, with Real Madrid’s Vinicius Junior their top target, a central midfielder and a centre-back to fill the gap left by an injured William Saliba.Bruno Guimaraes has informed Newcastle United of his wish to leave St James’ Park and join Arsenal, who have already seen an offer worth under £60million ($79.3m) rejected earlier this summer.Arteta has previously spoken about adding a different dimension to his squad, highlighting a need for more individual quality. Asked whether more business can be expected that brings those qualities to Arsenal, he said: “We are really active, trying to improve and evolve the team. That’s clear.“We expect to have movements in the next three weeks obviously because we want to get better like anybody else. You can just see the transfer market and what our opponents are doing. We won’t sit still. We are very ambitious in where we want to go.”Brazil international Bruno Guimaraes wants to leave Newcastle for Arsenal (CHANDAN KHANNA / AFP via Getty Images)This has been Arsenal’s stance since they lifted the Premier League title in May. They also reached the Champions League final later that month, losing in a penalty shootout against Paris Saint-Germain.On why there is still a need to upgrade, Arteta added: “Because the margins are very small and if you want to get better when the level is going to increase, we need to increase the competition internally. We need to make sure we identify the things we don’t have in the team to have bigger margins. That’s the way we have to think.“I think we have even more responsibility and ambition than before. We know what is ahead. We know the qualities and the capacity that we have to compete with any other teams. We need to prove that we belong at this level now.”Arsenal continue their pre-season by facing Real Betis in Dublin on Wednesday, August 5. They then host Borussia Dortmund four days later, on August 9, and Como at the Emirates Stadium on August 12 before travelling to Cardiff to face Manchester City in the Community Shield on August 15.The reigning champions then kick off the new league campaign at home against Coventry City on August 21.