I want to make a WordPress website in 2 languages (e.g. English & Bengali) without plugins. Currently my site is plain html with 2 folders. English pages in one folder and Bengali pages in another folder. How do I do it on WordPress without plugin? How to do it theme page/post?
A way my agency has chosen to implement it in the past is through subdomains. We created the entirety of our English site as you would normally in WordPress on mydomain.com, used the Duplicator plugin to clone the site to spanish.mydomain.com, and then changed all the text on the new site.
And as @MarkKaplun recommends, a multisite setup would be appropriate here as well, though slightly more complex. It lets you keep the same WordPress core for both sites, but different content.
An option is to use a plugin like WPML (which is generally considered the best plugin to use if you ended up wanting to go that route). However, there are issues as pointed out by @MarkKaplun such as the integration with other plugins and WPML assuming all content should be the same.