Confusion about vim folding - how to disable?

1. When I open the file it looks like this: or even this
2. When I open all folds, they are closed again when I navigated to another buffer and came back.
3. To be able to work with it, I have to apply zR each time when opening a buffer.

I have these set up in .vimrc:

set foldlevelstart=99
set foldlevel=99

Please point me on how to disable the folding, or at least making the navigation to another buffer not to close the opened ones.

You're not alone.

set nofoldenable    " disable folding

The easiest way to disable (and enable) folding on the fly is zi.

zi is the normal mode command that toggles 'foldenable', just like :set foldenable!.

Mnemonic: "fold invert". See :h zi.