sidebar not shown

Problem: no sidebar is visible after I changed theme to twenty seventeen (before I used graphene).
I searched elder forum topics about similar problems and understood (may be wrongly) I have to use a sidebar plugin and I tried to use them (sidebar manager light as well as custom sidebars) with no response on my website. As well the blog sidebar has never been shown. Although in Design-widgte I put widgets into the blog sidebar.
I need it urgently for some widgets like event calendar, and language switch as well as external links.
What is the main thing to to in order to make either the blog sidebar or another on visible on my page?
Thank you for help.

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