Are 3-kg dumbbells good for a beginner?
Yes, it's good for a beginner. But only for a short time.
Too light for dumbbell row, lunges.
It'll be less effective in terms of providing adequate stress for the muscles to grow after week 1 for doing bench press.
You'll breeze through multiple sets of shoulder press during week 2.
You'll probably be still using it during the week 3 for arm workouts and thinking about buying a heavier pair of dumbbells during the 3 second eccentric portion of the bicep curl.
By week 4 you're only satisfied doing lateral and rear delt raise.
By week 5 you will have already visited 2–3 gyms nearby after not having felt the "pump" in your forearms.