Is the battery backup the same if you charge with fast charging and charge with fast charging turned off?

I am faccing this. I get 4 hours of backup when I super fast charge. I also get 5.30 /6 hours of backup when I charge with super fast charge turned off. i use only with the box cable .My phone age 2 months.I bought Samsung 25w charger form Samsung ...

s25fe user who use 45 watt fast chargingand how is the sot? Do u recommend 25 watt charger?