I got warning in my iphone that the wifi from my deco is considered weak security. As per link https://www.tp-link.com/id/support/faq/2943/?app=deco i suppose to change the security setting in my deco

Hi, I am in Indonesia and just recently bough a notebook that strangely if connected to wifi from my Deco it can only get to 20mbps (my ISP bandwidht is 100 mbps), but if i connect to direct wifi from