2010 Ford Taurus not starting

I left my light on inside the car about 2 days ago
(Wednesday) around 9pm, after waking up
Thursday in the afternoon 12pm the car failed to
start, I had someone help me with giving my car a
jump it turned on and I drove it for like 10min came
back home and turned it off restarted it and the car
turned back on as normal.
Waking up in the afternoon today (Friday) the car
didn’t turn on but I noticed a symbol on the
dashboard of a vehicle with a lock, the symbol just
flashes and my lights inside the car are very dim
besides the dashboard lights and the radio lights. I
took it to a auto zone near me and they checked
the battery stating it just needed to be charged I
left it there for 2hrs came back and another
employee unfortunately told me it didn’t charge
and I needed to buy a whole new battery.
I’m not sure on what to do next or how to fix this
problem without having to buy a new battery
unless it’s my last option.