It is OK to leave your phone charging overnight as your phones battery will stop charging once it's fully charged.
The phone is equipped with features that shut off the charging to the phones battery once it's fully charged so there's no danger in overcharging your phones battery.
I leave my phone plugged in and charging overnight and all the time when I'm not using it and never had any issues.
You can tell how long it will take for your phone to charge by looking at the percentage of charge on the battery.
For a fully dead phone battery you should expect the phone to take at least 2 hours to fully charge and if the phones battery is only half depleted then it should take only an hour or sometime less to charge the phone to full charge.
To charge a phone to 100 it takes around 2 hours if the phones battery is completely dead and if the phones battery is only 50 percent low then it takes around 1 hour or sometimes less.
Charging a dead phone usually takes around 2 hours.
If your phone is only half dead and you have around 30 percent to 50 percent charge in the phones battery it may only take around 1 hour to charge.
You can also leave the phone plugged in all night or when you're at home and not using it to keep it charged.
When I'm at home I always keep my phone plugged into the charger to keep it fully charged at all times.
Never had any issues with leaving the phone on charge all day or all night.
This ensures that I never worry about my phones battery being too low as it will always have a full charge.
Your phone is equipped to turn off the charging to the phone's battery when it's fully charged so the phone will not overcharge if left plugged in and charging all the time.
It's best to keep your phones battery at least half charged instead of being completely dead too.