The Beginning After the End manga has indeed finished. It provided a satisfying conclusion to the characters' arcs and the overall narrative. Maybe there'll be spin-offs or related projects in the future, but for now, the main story is complete.
I haven't read it thoroughly, but generally, it might be about a new start that comes after an end in a fictional world created in the tapas novel. It could involve characters dealing with the aftermath of some great change or event and starting anew in that context.