Connected to WiFi, but no internet access

I was using WiFi normally on my phone. Then I turned it off, and after some time, turned it back on. Since then, I can not access the internet. It's showing > Connected (no internet access). I tried to set a static IP. It did not work for DNS 192.168.200.1. No matter what IP I set with this DNS, it does not work. Then I used 8.8.8.8 as DNS, now it's connected. But it is really slow, and the connection does not seem stable. Every time, I have to reload google.com several times just to get the page. The problem is specific to this device only. Other devices connected to the same network are perfect. Can someone suggest to me what I should do? Is this a router issue? Or is this my device problem? I'm new in this area. So my knowledge is not so deep, and you might have to explain things a bit more in detail for me to grasp the concept.