fuel gauge stuck on full

bad fuel sending unit

After filling up my Buick Lasbra gas gage stuck on full went on like this for a few months and a friend told me to disconnect the battery and let the computer reset itself which I did and this fixed it ....

Have 97 Buick LeSabre gas gauge been stuck on full from day one when I bought so I thought car had full tank while I was comeing down the road I noticed car starting to stall and the gas warning light in this particular car is a red dot that blinks one time and when u see that light the car automatically cuts off meaning it's out of gas dose anyone know what issue is or what's cause the gauge to stay on full how do I fix this issue