I am new to this fourm everyone in my family has a Benz beside me i still have a Lincon TownCar but i am having issues with my brothers car

Well My brother went on a trip for a two weeks i started his car ocassionally its a 2002 S 430 and now it went down to -30 i live in Canada. I boosted the battery let it run for 30 mins battery dead but thats not the problem when he was gone the front drivers side dropped down and it was touching the wheel i turned the car on it raised and such but now it says airmatic bring to gagrge or what ever it says what can be the case then today after i got the car started the messgae always stayed on the display and when i turned off the car it dropped a again i hear like a hissing sound of some sort but it only dropped a little not all the way. could there be a leak in the bag? Whats the labour and cost on that?

Thank you so much