If your car is taking too long to accelerate it could be caused by several different things depending on exactly what is happening when you accelerate.
If you depress the gas pedal and the car doesn't hesitate or sputter but your RPM goes up but your vehicle is failing to shift and pick up speed then your transmission could be low on transmission fluid or you could have contaminated transmission fluid or a clogged transmission filter.
Another possibility is that your transmission could be slipping and be on the way out which can lead you stranded on the side of the road.
If your transmission is okay but your car starts losing engine power or has poor acceleration or is sputtering then your ignition coil or ignition coils could be failing, you have low fuel pressure, partially clogged fuel filter, bad spark plugs, bad spark plug wires or you have water in your fuel.
I would recommend taking your vehicle to an auto parts store or Autozone or another shop and have them plug in a computer tester to see what the codes are which can tell you what is going wrong with the vehicle.