PHPStorm absurd behaviors

I tried to open an HTML file from a remote server. The "Open with" option does not find PHPStorm.
I then uninstalled Toolbox and reinstalled PHPStorm, this time "Open with" sees PHPStorm.
Nonsense.

I opened the HTML file, in default LightEdit mode, at some point I had to undo the last change I made but I got this error: "The following files have changes that cannot be undone: Problem file....."

I can't undo an operation?

I had to download Vscode, retrieve an old backup copy of the file and restore it. 
An hour of work for a change that would have taken no more than 20 seconds.

Then I tried to turn on full IDE mode, but it even asks me if I want to open the file in a project or in a new project.
Is this for real?

Should I use another editor to make changes?

I hope it is me doing something wrong, in case explain, thanks