Samsung Galaxy Tab 3 (T210) Slow Performance: Reset, CyanogenMod, Downgrade 4.1.2 & Memory Card

Hello!

Four years ago I bought a tablet as in the subject. It ran quite well (youtube videos in 1080p, games like angrybirds go or mortal combat) everything worked fine. After about 3 years, problems began to occur, the tablet slowed down a lot, then I changed the tablet to Alcatel from Orange. After half a year, the Alcatel tablet broke down and went to the garbage. I took it, for tab 3 I reset the system 15 times, it did not give anything, so I decided to upload Cynagogenmoda and again nothing. I even downgraded to 4.1.2 (stock) and again nothing. I turned it over, switched the applications to
memory card. I removed unnecessary Samsung software in the programming options, I set no background processes and the animation scale to 0.5x, then nothing. I'm losing hope 720p movies are stuttering every few seconds, the sound stutters. I'm not even talking about the browser. I am asking for help because my hands are dropping, what am I doing wrong, that's how it is.

I like this tablet the more that it was bought and removed from the packaging all the time in an armored case and tempered glass.

Greetings Piotr.

Maybe the problem is not with playing movies and the Internet?
I used to have that too and changing the wifi channel on the router helped.

It is not it. My Wifi is fast (80mb's). On other phones, everything runs smoothly even in uhd. And the problem is not only with movie playback but with everything. Even the simplest games don't run smoothly. I used to play Angry Birds Go without lag.

greetings Piotr

Remove unnecessary applications, install anti-virus and scan.

I have installed a brand new 4.1.2. There were also modding attempts, nothing helps.


Edit:
The problem is still valid.