Hello iUltimateLP,
Thank you for your questions. I will answer your questions in order:
When I pay 20€, it is for one month. If I don’t pay for the next
month, I simply don’t have the
subscription anymore for UE4, or
should I cancel somewhere the plan?
You will have access to all of the builds that were available to you during your subscription, even after cancelling. Your continued subscription will simply ensure you get the latest updates and content. Cancelling will not stop you from accessing the versions of the engine and content that you already had access to.
When should I pay? At the beginning of a new month, or when exactly one
month is over, for example if I pay on
the 15. of March, I have to pay again
at the 15. of April?
Whenever your subscription is over, then you would want to pay again. So your example of “15th of March to 15th of April” would be accurate.
When should I pay the 5%? Together
with the other 20€?
You would send in the payment separately. Here is the guide and more information on making royalty payments:
Let me know if you have any additional questions.