Hmm, that can be a challenge; to figure out, what is going on. Being in Poland and not having a VW of France dealer support; might be tough, to figure things out. Here, in the USA, many people; install, incorrect used parts on VW's and it causes problems. You might want to contact a VW dealers parts department, in France or Poland with your VIN number and confirm, that your speedo cluster, is the correct part number, for your particular car.
A new cluster might be a option; if it is incorrect or if correct, having the cluster repaired by a specialist. Bosch, in Germany, offers, a repair service; for various electronic modules, that might be a option? I guess, you should confirm; it is the correct part number and then, see, what the cost of repair or replace with new is?
The benefit, of having the speedo repaired; is, that no programming, would be required by a VW dealer or VW specialist, for the cluster or the immobilizer, keys adapted.
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