Repair selebr possible?

Siemens EQ 6, series 300

Hello, I have above machine for 3 years and about 4 months. A week ago the machine was still making coffee, then all of a sudden it only starts up briefly, the display goes on and off again. Taking the power away for a longer time does not help.

I have always done calc and clean regularly, in the beginning with Siemens products, afterwards here with:
https://www.ebay.de/itm/50-Reinigungstabletten-15Entkalkertabs-pass-fur-EQ3-EQ5-EQ6-EQ7-EQ8-EQ9-Siemens/224144891290?hash=item3430139d9a:g:9qEAAOSwYl5fgGP~

Now I have taken my machine to such a coffee repair shop, they say the machine would be calcified inside, very and some valve and the brewing unit would also be gone, so the brewing unit calcified.

But now another shop on the phone told me, the brewing unit can not calcify at all, I am now completely at a loss.

Actually I had given them the repair order, is supposed to cost 180 euros, but they always tell me, so older people, I should ask again at Siemens, there it costs 210 euros. Why I do not understand so right, as if they do not want to make the repair...she said today still, it could then aj also what else will break again soon?

Oh well, now I have to figure out what to do.

Do you think you can somehow fix it yourself by buying a new brewing unit and can you somehow decalcify the inside differently? Does anyone know this error? Thanks...
LG Fee321