Engine is not pulling properly

so, again a little problem where I want to ask here first. So what happens? when the engine is cold, it runs at full power. But when it's warm it spins something, and it does: when giving gas it comes well, but it pulls back for a short time, then it gets full power again, but only briefly, then the same again. And so it changes. always gas, and again a little less. Nevertheless, my sprite consumption is very low in urban traffic, 14 - 15 liters. Does anyone have any idea what that can be? would like to be able to give gas without someone pulling me back :-) achja, in the gearing (s) it is less striking.