PS4 is lagging regularly even though I have good Wi-Fi?

I would like to ask you what can be the reason that my PS4 is often out of bed, even though I have good Wi-Fi at home (for example, it works very quickly with my smartphone and is not out of order). In games like Call of Duty or especially Fortnite, my PS4 is often (at Fortnite, I usually have a 20 ping, which often shoots up for no reason and is then to 200 and soon goes down again). Is that due to the WLAN or can it also be due to my PS4? This is namely about 6 years old and the first model that came out (not the Slim or Pro)

Well it's still Wi-Fi and no LAN. So, as long as you don't have the transition, lags can always occur.

WLAN fluctuates, but LAN tends to be less or not at all.

So I would recommend at this point if it is possible for you to wire a LAN cable from the router to the Ps4