One of the things you’ll need to consider is that browser list a series of languages and preference scores, so you need to resolve that to the languages you’re supporting. e.g. if they’re en-GB you might have en-GB or you might fall back to en as your default.
For a full multilingual solution though the trickier part is tagging and managing your content. For sites which need a simple multilingual capability with only 2 or 3 languages, this can be done directly in your content strings and by using custom attributes for tagging.
For anything more complex, you’ll probably want to look at Linguana or Weglot.
Yes I can build a multilingual feature for you if you want but it’s a bit of work, you can direct message me if you’re needing that. I suppose it’s a good approach, it would cost you a bit up front but a lot less than the ongoing fees of a multilingual platform.
You might also check this library I built as a solution about 5 years ago, it has the capabilities you’re looking for but the documentation is thin.