Bumps at the beginning of the layer

Hi guys,

I have recently got Creality CR 10S and my models are having some problems I don't know how to solve. They have some little bumps on the surface and in the slicer I can see they all are likely on the beginning of the layer or on the end of a travel movement. Halving the speed and acceleration of travels and the acceleration of walls some improvement can be seen but I can't get a perfect result. Y have tried to tense the belts but it didn't work. Does someone have any advice for me?

try enabling retraction between layers.
Most slicers don't have it on by default.