What’s the best approach to do this?

about the permalinks you should go to settings->permalinks and change permalinks to “post name”. then you can see “/blog/” for your blog page.
for translating your theme you dont need any plugins. you should work with .po files. go to your theme folder and then “languages”. there you can see translation files inside this folder. you can create your own translation files but actually you need a software like “poedit“. it’s free to download and use. good luck