What's wrong with this square ceiling light? And how to remove the light fixture and replace the bulb?

Hi,

New and clueless home owner here.

I have what appears to be an LED ceiling light in my living room/kitchen, controlled by a ON/OFF switch: https://imgur.com/a/f0vNxZS

I used to work fine. A few months ago, problems began to occur. The light would be dim when switched on and would take a while to suddenly pop into (its normal) full brightness. Initially, it was a couple of seconds. Then, it turned into minutes. Then it turned to 4 hours. Now, it never reaches full brightness and just stays dim all the time. I have to use a candle.

I need to take care of this. It will be my weekend project. I guess the first thing would be to remove the cover. But how would I do it?

I have used google image search and found some results that match what I have, such as this one: https://www.amazon.ca/CHENKUI-Adjustable-Three-Color-Lighting-Energy-Saving/dp/B09H4KHWQ4?th=1

However, I have so far been unable to find any user manual on how to remove the cover, to see what's inside and to change the bulb.

Any help would be appreciated!!

Thanks!!