Do manga artist usually planned an ending before starting a series?

Do manga artist usually planned an ending before starting a series?

If they do it's probably pointless, since 95% of new series would be canceled before getting close, and the other 5% the publisher demands it continue past the "ending".

The major story beats are planned, and the editor gives them notes to fill the stuff in between. Sometimes things don't go according plan for a number of reasons like time constraints or even a character's popularity.

Commonly yes, its when the popularity kicks that editors ask for more content deviating from the original concept. Try appealing to sell or be irrelevant.

Publish or perish is the japanese manga motto. If your shit is selling it ain't stopping unless you wanna eat ramen in the streets.

fuck no

I think in general, yes they do. There's a few cases where authors have dropped a series because they don't know where they're going with it, or they've written themselves into a corner.

If the series is popular, they might stretch it out, add and rewrite parts, but I think most popular authors know the ending pretty early into the series run. I know Oda has stated multiple times that he's already written the ending, and Nakaba had the general outline of his beginning, middle and end before he even drew the first chapter.

Depends on the series and author, like most other forms of media. Some plan meticulously while others make shit up as they go along, there's no universal pattern or method to it.

Why do manga artist draw landscapes like this. It's unnecessary and a huge waste of time.

Because they pay assistants a pittance to do this shit.