PS5 lag while playing online (despite a good connection)?

A couple of days ago I finally got my PS5. Everything is going great except for playing online. Whenever I play a game online I have severe lag every 10-30 seconds. The strange thing is that my PS5 can download YouTube videos or games without any problems, but the connection gets worse when playing online. I've tried everything: release ports, 5Ghz frequency band, change DNS, change WLAN channel. The game servers or PSN are all online and have no problems. My Wi-Fi works fine on all other devices. I have no problems playing online on my old PS4 Slim. I even played online on my PS4 while downloading a game on my PS5 and I had no problems there.

According to the connection test, my PS5 has an average of 50Mbit download and 10Mbit upload. I'm not sure what to do next. Is my PS5 broken? Should I replace it or claim my money back? As I said on my PS4, I have no problems and my PS5 is even closer to the router. Does anyone have such problems too?

Have you restarted the router before? In the beginning I had problems at the parties when I gambled online. A reboot fixed the problem.

PS5 hang over Lan cable ran.

But why do you think it's the internet? Couldn't it be frame drops because the console is getting too warm?

No, when I play offline it doesn't happen. And with Warzone you always see symbols on the left if you have connection problems.

Have restarted the router several times, but nothing worked. It works fine on my old PS4 Slim.

But why should I connect it via LAN if my PS4 works without a LAN cable without any problems.

To test whether it is better then. Or whether the error comes from something else.

Could it be that the games you want to play simply have overloaded servers? I have the same problem with Warzone, MW, Valorant and co. These games are of course very stressed by the lockdown

No, it can't because they run on my PS4 without lag or disconnections.