Which dumbbells should you choose?
The weight you use depends on your skill level and the muscles being worked.
There's a right weight for every skill level. You should be able to complete your reps but be tired at the end.
Lower body muscles (thighs, glutes, etc.) are comparatively larger than upper body muscles (shoulders, biceps, etc.)
This means you should choose heavier weights for squats and lunges (2 kg and up) and a lighter load for smaller upper-body muscles (1kg)