Having used smartphones since 2007, and using most of them for a good 3 years before switching out, and even then, a few are still around used by my kids a few more years, I've found the advice "don't keep on a charger once you hit 100%" to be utter nonsense.
Cell phones have had the ability to reduce the incoming charge as 100% is reached, and completely stop charging at 100%. Until it drops a bit and a trickle charge is applied to slowly bump it back up and stop again.
This has been a thing for nearly 20 years with Li-Ion batteries. My batteries have kept their charge capacities well into 3 years of use before starting to show quicker discharge rates. And that's about normal for Li-Ion batteries in general, regardless of all the OCD-based hysteria about battery life.
Charge it up as needed, use the device as needed. Charge it up again as needed. Live your life.
I keep my S24+ on a wireless charger all night. Pick it up in the morning. Work all day, and use it for several Teams meetings during the day, come home, drop it on the wireless charger at night. Wash rinse repeat. By the end of the day, I'll have anywhere from 50% to 30% left depending on how much I used the phone for conference calls that day. Did this with my S20 FE before that for 2 years. An S9 for 2 and a half years before that. An S8 was on a wired charger but hitting the asphalt after having it for a year is what took it out. Before that, I had a BlackBerry Z10 on a wired charger every night for 4 years. It did start losing capacity at the 3 and a half year mark, but I lived with it that way by topping it off before leaving work or charge it in the car on the way home.
By the way, the S9 is what my son is still using today, and the battery in it still lasts the whole day.
There are things that can degrade the battery sooner. Letting it get hot, and staying hot is not great. Also, letting the battery die too many times can shorten the life.
However, the idea that you need to discharge it completely once in a while is totally false. That was advice from the older NiCd (nickel-cadmium) battery days. Those batteries did have a "memory" such that recharging before it was depleted would reduce its capacity. Li-Ion batteries in modern cell phones have no such issues.
You must of gotten a defective one because phones already have battery protection once it gets to a certain percentage it stops the charging one of the best futures for the ones that forget their phones on the charger
Yall people need to mess with yall phone settings close any background apps not being used optimize your phone turn on battery protection power saving your phone will be fine
