Connection problem with WIFI

I’m experiencing an unstable Wi-Fi connection and high ping (MS) on my iPhone, which sometimes prevents me from searching on Google or watching Instagram Reels. I’ve tried many solutions, but nothing has worked. I changed the DNS settings on the router and adjusted the network settings on my iPhone multiple times. I also disabled background apps etc…, but the issue persists. This problem only happens on my iPhone (an iPhone 15 Pro Max, which I bought in October), not on other devices. Could you help me fix this problem?