It's true that the weight upstairs is small many times, but your group number is too small, there must be at least 5 groups.

The main exercise of lifting like that is the shoulder of triceps brachii, and this is the following action.

One-handed dumbbells are placed under the back of the head, and the big arms are perpendicular to the ground. The forearm moves upward from the back of the head until the arms are straight. 15-20 group, one for each arm, make 4-5 groups.