OK, I'm looking at the English translated version in the Google Chrome browser (Version 54.0.2840.59 m) on a Desktop system with HDMI@1080p on a 32" Samsung Monitor. (I'm sorry, I don't have the time to look deeply @ it in mobile right now, but from what I saw in the Chrome emulator, it looks nice.)
I like how clean the site looks. You have a nice, clear and professional Hero Image of Mr. Friedman in the header which is a good intro. I'm not a big fan of collapsed "Hamburger" style menus on Desktop layouts, but that just me. In the menu, the "t" in "Training for Executives" is lower case, an easily fixed item. I'm a fan of "About Alexander Friedman", than just an "About" section... more for Organic SEO purposes than anything else. Especially in H1 tags. In fact, any "branding" you can do in the navigation without over-doing it, is great for SEO.
Social icons in the upper right-hand corner look good and clear. The sub-menu looks fine, with exception to the one item "Training for Managers of". Managers of what? Could be a translation issue in Chrome.(?)
Upcoming events looks nice, as does the book panel and "New Blog".
In the "Contact With Me" panel, there is a huge sea of white space to the right. I think this would look better if you pulled the "Follow Me" section up to the right and did a column list of social sites by name, social icons that match the ones in your top header (or both). Easily done in Flexbox.
"Delivery" and "Let's start a conversation" areas are nice, but in the English translations, the forms' fields are still in Russian(?), but if the US isn't his market, I'm not sure that's a concern. Also, the "D" in "delivery" is should be capitalized to follow your established section formatting, but could also be a translation issue.
The sub-footer navigation has the same issue as the "Contact with Me" section. Huge right-hand white space that's again, easily fixed with Flexbox. "Consulting" and "Publishing" could be a middle column here."Customers and Partners" could possibly even get more of a listing of linked business names than just one general link. If there are many, then "Consulting" could just remain where it is in the first column.
I did look over the rest of the site, however, I didn't have time to go too much deeper into it like I did on your entry page. I did notice a capitalization issue on the sections of the website, most likely due to browser translation, as well as more odd sub-menu items, which I'm again attributing to a translation issue.
Over-all, I like the site... the header image fade transition is nice and smooth. You made this guy look professional and classy. Well done!