my transmission on 2005 BMW 645Ci

i was sitting with my car ideling an all of a sudden a warning flashing that my transmission would only shift from reverse to 1st an 2nd gear an when i drove it those where the only gears it would drive in i added transmission fluid from the neighborhood store an it drove for a day an went out again

Asked by for the 2005 BMW 645Ci
By all means take your 645 to a very good transmission shop.