Rewriting URL for SEO purposes

Hello,

I am working on a multilingual website. To determine which language needs to shown, I pass the variable $taal in the URL. (“taal” is Dutch for “language)

Examples:

1) https://ruylclassics.nl/menu/?taal=NL
2) https://ruylclassics.nl/ClassicCars/mercedes-500sl-r107-oktober-1981/?taal=NL

Now I would like to have these URLs rewritten:

1) https://ruylclassics.nl/NL/menu/
2) https://ruylclassics.nl/NL/mercedes-500sl-r107-oktober-1981/

At 1) the variable before the page name (can be other pages) and
at 2) the slug ‘Classic Cars’ (CTP) must disappear

I’ve tried a lot of stuff (editing .htacces, add_rewrite in functions.php, …), I’m Googling all day, but unfortunately without success.

This is at the bottom of my .htacces-file

# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>
# END WordPress

Can anyone help me please? I would be very grateful!

Kind regards, Bart