307 1.6 HDİ Gas Cutting Problem

friends, I have 307 1.6 hdi .. In the 3rd and 4th gear, 2500 cycles in general, while going uphill, cut the gas and leave the car slightly haggling back. Does anyone know what is the reason for this?

My 1.4 HDi 206 is the opposite. For example, while going uphill in third gear, as if you pressed the clutch and downshifted in 2000 revs, the rpm rises and the car accelerates, then the rpm decreases a little and starts to go normal. All this happens while pressing the gas hard. I wonder why is it a normal feature? The vehicle acts like an automatic gear you know.