For changing the language of the file browser:
As an alternate to what ZimSystem mentioned (override the CSS), a more elegant solution is suggested by the bootstrap docs: build your custom bootstrap styles by adding languages in SCSS
Read about it here: https://getbootstrap.com/docs/4.0/components/forms/#file-browser
Note: you need to have the lang attribute properly set in your document for this to work
For updating the value on file selection:
You could do it with inline js like this:
<label class="custom-file">
<input type="file" id="myfile" class="custom-file-input" onchange="$(this).next().after().text($(this).val().split('\\').slice(-1)[0])">
<span class="custom-file-control"></span>
</label>
Note: the .split('\\').slice(-1)[0]
part removes the C:\fakepath\ prefix