l have a jeep cherokee 2004 2.5l petrol sport but why are they so slow

It should be a 2.4 petrol or a 2.5 diesel, but basically, 4x4 vehicle is engines are tuned for torque, not power. This makes them feel pretty sluggish, especially with a very heavy body to lug around. The 2.4 petrol produces 145bhp and 159lb-ft of torque. The 2.5 diesel in the same vehicle produces 141bhp, but the diesel engine is actually lighter & produces 252lb-ft of torque, making it feel a lot more lively.

well because its a 2.5

It is a fairly gutless low-tech engine and the Cherokee is a very heavy, un-aerodynamic car.
You really did not buy it for its speed anyway, did you?

One word: WEIGHT!

Whilst the Liberty , for that is what you have, not a Cherokee, is not a very big 4x4, a 2.5 engine is still rather small for the weight and the drag of the body style.
Speed need power, and you have not got a lot !

because they have no green ooze in the engine