real hard start when trying to stop car seems to rev up slip n vdc off lights o

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Problem just started last week car wouldn't start after trying a couple times left alone called tow truck next day they jumped it n said it was battery I took it to mechanic they said it wasn't the battery n not sure what it was computer had no codes when I picked it up I heard a boom sound under the car the vdc off n slip lights r on its starting but u got to hold the key over a while before it will start