RM4

LESIMOON, your solution works fine! Thanks a lot!!!

Thanks to all.

Jan Dembowski, I am using Child theme. So I can edit child CSS without any losses after update.

This code was added by me because width: 100%; or max-width: 100%; – does not helped and width come to 331 px.

I can replace it. Pls advice what should I paste.

Sure. Main page of web-site.

Main page (in the bottom) https://strij.net/
Inner page – https://strij.net/online-monitoring
Inner page – https://strij.net/internet-of-things/resheniya/vashe-reshenie

max-width: 100%; – also does not have effect –
Width come to 331 px – https://joxi.ru/YmEkB5iZGL6EA6

https://strij.net/tehnologiya-strizh/feed – same