how to improve latency? buy better router?

i have 500mbps unifi but sometimes competitive gaming got random lag/ping spike and rubber banding that one why ah?

and whats make you think the current ISP issued ax3000 router cant provide 800mbps via wireless?
my parents also use 800mbps package la, bammm 800mbps speed test, but within 10meter from the router la.  skyworth or fiberhome brand, i dunno cant remember. the previous were ax1800 fiberhome brand, 500mbps is easy there.

my father got ax3000 router from TM also because of the recent speed upgrade exercise, changed for free because the previous router are deemed not good by the ISP.\

here the speedtest with TM D-Link DPN-FX3060V combo router