Sitemap questions

Actually I have two questiuons.
How to change index file’s url from http://www.georgia-tours.eu/sitemap_index.xml/ to http://www.georgia-tours.eu/sitemap.xml/
So if it is not submited usually everybody looks for sitemap on this location.

I have 2 lingual site, using polylang.
So I have 2* quantity of posts, pages and categories. So normally if I have 45 posts, in sitemap there shall be 90 posts, but there are no, so not all posts, pages, and categories are included. I checked sitemaps and both languages are included, but only 30-40% of overall quantity. how to fix it?

https://wordpress.org/plugins/wordpress-seo/