Good day to everyone, react\next has recently started studying. I've been trying to figure out multi-lingual for a long time and something new pops up all the time (problems)

here's the last thing I did (link to the sandbox):

https://codesandbox.io/p/sandbox/next-js-intl-3-0-beta-tdw7sx

almost all my tasks are covered, but there are still little things that are not so petty ..)

I promise the task I have is this

1. there are 2 languages (one Arabic with RTL, while for the convenience of rtl I have ru)
2. I want the select drop-down list to show the current language when updating the page
3. switch buttons ru > en, so that some class is added to the active language, for example, or some other way of implementing language switching (buttons, links) - so that the selected language is saved when the page is updated.
(now the language seems to be saved in cookies, when closing and opening the page, the last selected language is displayed) - probably new in intl-3.0

4. I could not figure out how to add an active class for an active link to the main page, page. without multilingualism, everything turned out to be done..

please help me figure it out