Translating website to Russian, blank homepage issue

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Hello all,

First let me tell you I'm not very profficent, not to say I'm a newbie in concrete5.
My website is currently working in two languages, but I want to add third translation.
When I try to do it as I learnt from tutorials and videos, I created a new site in Sitemap (tried both- blank page and Main page) name it to "RU", went to multilingual settings and changed the RU site to language site (it has a flag now and I can pick it from my frontend menu).
Afterwards I copied the site tree and.. the homepage of the new translation goes blank. It views only 1 blank button and 1/15 of the background.

I found a solution in here, someone firstly copied the Mainpage of another language into the "system files tree", change the name, and move it to the sitemap.
I tried it and the result was a little better- page looked normal up until i changed it to the language site, all the menu buttons disappeared.

I am almost sure that this is a really minor issue and I probably don't tick an option or I missed something, but Im struggling for hours now so I'd really appreciate any help!

All the best
Damian