(Please ask one question per thread.)
[ol][li] The insert key toggles selection of the current item and then moves the keyboard focus to the next item. If you push insert on something that is already selected, it will be de-selected before moving to the next file.
You might want to turn off Preferences / File Displays / Options / Automatically select first file in folder (except in Power Mode), if it is on.
[/li]
[li]Except for a few special cases, like folders and junctions, type names come from Windows and the language they are in will depend on your system langauge and also which languages are supported by whatever software added those types to the system.
(If you think about it, Opus cannot know the names of every possible file type that might appear, e.g. ones that are made up by other software that Opus knows nothing about, or even file types that haven't been invented yet. The names have to come from somewhere else, so they cannot be tied to your Opus language choice.)[/li][/ol]