What's going on

You may ignore this, I just wanted to rant out of extreme frustration. I am a beginner chess player, and play mostly bullet. I was able to achieve 1100+ rating in it, but recently my rating is constantly falling down, and I have no idea why. I play on lichess.org too, and I am able to maintain my ~1600 rating there. On chess.com I however start to feel like the outcomes are completely random. I often lose games because of flagging out of the blue (I may be imagining things, but I feel like there is something wrong with the timing implementation) and recently the new trend appeared: I start to lose to 700 or even 600 rated players. I can win no problem against the 800 rated players, but not those with lower rating. WTF…

Everyone goes through ups and downs. If you look at your history over the last year, you have had multiple sharp declines. It appears that you always climb back out of them.

Be patient. Get a good night's sleep.

Correct, but if my game is in decline it should affect performance everywhere. But yet I fall here, but not on lichess for some reason.

What is your play ratio like between the two sites? Perhaps Lichess is a smaller sample size.

Lichess ratings are often 500-600 higher than here, especially at low ratings.

When I read, “beginner … mostly bullet”, I had a diagnosis before looking at your games. Looking confirms the diagnosis. Slow down. Learn basic checkmate patterns and tactics. You miss things nearly every game.

Your server sucks.