1988 Mercedes Benz 190e

I started having problems a few months back with Transmission slipping or not engaging into 2nd gear, I changed tranny fluid and filter yesterday and read wheer the transmission and converter hold somewhere between 6-7 quarts of tranny fluid, my question is I changed fluid and filter out about yr ago and had some occuring problems with shifting or slipping and my question is how many of the 7 quarts does the converter hold since both times I removed tranny pan and changed fluid and filter I only added 3 quartsand keep getting inaccurate readings on the dipstick. Some people are telling me I am way low of fluid since it will not shoft after 1st gr. Now ehen I leave it shifts and nerve shifts into 2nd bu RPM's climb till I remove foot from accelerator?