Paint with light

The new thing now is to take pictures at night with a technique that we call painting with light.

This is a technique that I am completely in the start phase so here I have a lot to learn.
You take several pictures in a win and put them together in PS later. For example, I use the following setting on 1 image and the rest.

Picture 1 -: eg 20mm 1.8, F2.5, 20 sec, ISO 2000

Picture 2 and beyond: 20mm 1.8, F5.6 20 sec, ISO 500

The pictures must be taken with a stand.