Does the Xbox Live Gold subscription continue automatically?

There's currently an offer in the Microsoft store: One month of Xbox Live Gold for 1 euro.

Now my question: If I now subscribe to this payment and pay the euro, will it be extended immediately after the month and will I be charged more money? Do I have to cancel the subscription directly so that the said thing does not happen?

Yes, I think you have to cancel in time

Everything is in the purchase contract that you get presented. Just read it through and you know it.

Yes you have to quit otherwise it will continue to run automatically.

Hence, as you correctly described, "this subscription". So you can actually draw your own conclusions. Otherwise it would not be a subscription.

This is precisely why there are such attractive lure offers. So that the tempted buyer gropes in the waste.