Extending Ceiling Lamp Cables Safely: Electric Connections, Moving Light Points & Adding 0.5 Meters

Hello!
I have this problem: I need to move the light points on the ceiling by about 0.5 meters, which makes it necessary to extend the wires. I'm going to do it by adding the same size cable (I will connect them with a cube). I wonder if this connection is electrically safe? Or maybe there are other better ways to do this cut?

Thanks in advance for any suggestions

You can, for example, solder and put on heat-shrinkable sleeves.

Do you want to embed them in the ceiling or just extend them (and leave them in the air)?
In the first case, I recommend the method given by the colleague, it is best to use T-shirts with glue or add "sealing" with thermal glue.
in the second (apart from aesthetic considerations) cubes are enough.
Greetings J.

thank you for the info.
I would like to embed it in the ceiling - hence, due to the dimensions, the T-shirts are the best - I only have a question - T-shirts with glue - what is it, because so far I have only seen heat-shrinkable ones?

T-shirt with glue is a combination of an ordinary heat-shrinkable T-shirt and thermal glue in the so-called chopsticks, it is softened with a special gun with an electric heater.

T-shirts with glue are a combination of both inventions, the T-shirt simply has a layer of this glue on the inside. As the T-shirt heats up while shrinking, the glue inside it also melts. Cooling down causes the adhesive to harden ...

Such T-shirts are used for min. cable joints that are in the ground ... Proper connection and welding ensures 100% tightness.

If you want to plaster / brick the cable, I would choose the more reliable option, i.e. tight twisting the wires and soldering them, after pulling the thermo-tube with glue. This will ensure reliability and low connection resistance. However, if the cable is going somewhere overhead (above the suspended ceiling), you can, of course, easily give yourself a cube.
Regards!