Seal the joint between the gypsum ceiling and the wall?

Hi,

my name is Markus, 47 years old, and I am a locksmith by profession.
We have recently built a new house. Painting work is being done by us. Unfortunately, I filled the joint between the plasterboard and the plastered wall with filler, resulting in severe cracks.
I have now scraped out the filler and wanted to ask about the next professional step. The joint is now 3 to 6 mm wide. Thank you in advance for your help.

Regards, Markus

Buy Kurt Fugenband and fill with putty.

I was advised against using the Kurt Fugenband by an acquaintance, I have seen the ceiling-to-wall joint myself. The tape detaches from the plaster and/or tears. Does anyone have another idea?

I had written something at first, but was warned for it, no idea why. Allegedly off-topic and without added value, even though they were tips specifically for the OP. I'll try again, rephrased. The joint has cracked because the plaster behaves differently than the concrete. So either a flexible joint (silicone or acrylic), but that is a maintenance joint and must be renewed regularly. Or work out a shadow joint (keep the joint clean and uniformly sized everywhere). Or glue ceiling moldings (on one side).

Since the joint is not exactly small, can I already inject and smooth the acrylic now and then wallpaper afterwards? Does it make sense to apply the acrylic in 2 layers because of the risk of cracking? Thank you very much for the answers.

I was advised against the Kurt Fugenband by an acquaintance, I have seen the ceiling-to-wall connection myself. The tape detaches from the plaster and/or tears.
Does anyone have another idea?

Not processed correctly. If properly filled, nothing will tear there. I have over 40m in my place without any problems. You won’t get a visually better finish.