Hi @Attila Kecskés, a new place! Unfortunately the speed of the internet connection is a little less. :( 

Well you can move your subcription to the new adress. You can also downgrade it then to a 50 Mbit/s if more it's not possible. So you won't pay for the speed you can't use. 

But 50 Mbit/s is very little for me.
Is there no other option?

The other option is going to Ziggo which uses a COAX connection or a local fiber provider if it is avaliable

Yes, but I have a contract with KPN until January.

It's a grey area... KPN can provide you with internet/TV on the new adress, but within your current contract bandwidth. According to their Terms, you can stop the subscription when KPN can not deliver anything on your new adress. But that is not the case.

My advice would be to call 0800-0402 and use the word "opzeggen" to be connected to the proper departement. Then explain the problem and that you really need more than 50 Mbit. With some luck, they will cancel the subscription and you can go to Ziggo for the new adress.

If not: 50 Mbit could be quite enough for daily use untill january. Including Netflix/working from home etc.. you might be surprised as to what the real need for speed is :-)