Audi A6 2006 problem with battery

Yes
First thing is to test the battery and this is how Turn on head lights, if dull leave on to see how long the stay on for. Next turn lights off put battery on charge for 6 hrs .Turn on lights again if still dull either battery or charger no good
If lights bright try to start and when starter trys to turn engine over the lights go dim THEN battery is no good.
Then get a jump start from another battery and put pos term on both batterys first, then earth lead(BLACK) on last then start if starts ok remove the BLACK lead and turn on head lights if goes bright ALTERNATORs ok so replace battery ....