Insulation of floor-level shower

Good day everyone,

how should a walk-in shower be insulated?

We have the following problem:
Water damage in the bedroom (stains, laminate warping, etc.), water is coming through the adjacent wall to the bathroom/shower.

Two people from a renovation company were here, who work hand in hand with the insurance.
The first person (measurement technician) said that the silicone joint (wall/floor) was porous and leaky, that maintenance must take place and the insurance will probably cover the consequential damage, but the joint has to be replaced by us. He further said that there must be insulation under the tiles that holds the water in the shower. The silicone joint is just cosmetic work, but the waterproofing of the shower must be ensured even without an intact silicone joint. He suspected that the insulation (8-year-old house) might be damaged and that tiles would have to be removed to check it. He measured moisture everywhere in walls and floors.
He finally said that the joint repair is a short-term solution; to keep the water in the shower room in the long term, the insulation must be checked.

About three days later, the expert came who had the measurement results. He said he still had to check them and could not say anything yet. He took photos and some measurements.
Now the report has arrived, or directly linked with an offer for renovation, which is usually covered by the insurance.
I was told during the inspection that furniture (in the bedroom) would also be disassembled, stored, and reassembled. In the offer, it says I have to do that myself. I can move a dresser, yes. I cannot push a 3-meter-wide wardrobe out of the room, nor can I assemble or disassemble it. Is that usual?

Furthermore, the offer states that all work (drying, replastering the wall, painting, changing floors, etc.) will take place in the bedroom, since we have to take care of the silicone joint ourselves. However, I wonder if it is enough to just renew the joint in the bathroom. The first employee told us that the insulation must also be checked, since the water in the shower must remain even without an intact joint.

As it is, there are links saying this or the opposite, and of course everyone in the family thinks they know better (no tradesperson).

What is your opinion?
Sorry for the long post, I hope it was understandable.
Thank you very much and best regards!

The silicone joint is just cosmetic work, but the watertightness of the shower must also be ensured without an intact silicone joint.

Absolutely correct!

However, I wonder if renewing the joint in the bathroom is enough.

No, because the underlying problem remains and (perhaps) will occur again at some point.

The question is who must fix any possible construction defects. Is that really covered by insurance?

Attention, this is purely my assumption: The 5 years "Gewährleistung" for the usual accidental construction defects have expired. However, if the shower was never properly sealed, this is a hidden defect for which the executing (Sanitär?) company can still be held liable.

The first employee (measurement technician) said that insulation under the tiles can also crack or be damaged similar to the settlement cracks in the neighboring room due to "movement" of the house.

From what I hear here now, I should discuss with the insurance damage assessor on Monday that the insulation in the bathroom also needs to be checked and the tiles in the shower have to be removed, is that correct?

As I understand it now, I should discuss with the insurance claims adjuster on Monday that the bathroom also needs to be checked after the insulation and the tiles in the shower need to be removed, is that correct?

That is the right decision.