Posts template (style) broken

Hi,

I have a static Front page which goes to a link in the menu called Posts, which displays list of excerpts of three latest posts. Each post has a Read More link, which goes to a permalink, i.e.:

<a href="<?php the_permalink() ?>" class="more-link ">Read more</a>

I styles Posts page. If I click on Read more, I can see the header and footer are loaded, but the style of the main content containing the article itself is completely broken. Not even the body background is correct.

I tried to change in wp-admin, Settings, Readings, A static Page, Posts page to the page Posts, which was alredy correctly styled, but after I save the changes, I face to the same problem, only even earlier, not just on the Post detail.

Can anybody, please, tell me, how to fix this problem?

Thank u!