Thank you for sharing your experience and tips. In the meantime I took a closer look on the G-codes generated by Creality Slicer. Within the set of starting commands there are lines:
G92 E0 ;zero the extruded length
G1 F200 E3 ;extrude 3mm of feed stock
G92 E0 ;zero the extruded length again
It's setting 0 position for the extruder and while doing this it's extruding some amount of the filament (here 3 mm). After deleting these lines, filament was obviously not extruded in such as amount as before. I found also a similar tip on this forum yesterday ("Ender 5 Plus Extrusion Too Early") - exactly the same prolem with filament was discussed there.
I had also the first contact with Ultimaker Cura slicer and it's indeed far more powerful than the Creality one.