Juan-wrote
1. It's the rel="canonical" tag. I still haven't figured out where to place it.
you still have the canonical wrong
you have
<link rel="canonical" href="https://psydopomoga.com/index.html">
it should be <link rel="canonical" href="https://psydopomoga.com/index.html/">
Or even better
Correcting the system that generates duplicate content in the first place is the best solution.
I can't see how your folder system deals with the two languages, or where the choice is for people to select the alternative Russian language
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(you have declared Ukrainian as the primary language, you should probably make that a custom declaration setting both languages
<html lang="uk ru">
If I was you I would drop the canonical thing altogether for the moment until your website id FULLY finished and operational, because if it's not done right (Either way) there is a chance that Google (and others)( will DE_INDEX the site altogether, making it disappear from search engine results pages altogether, which can then take absolutely ages to get back indexed
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