Articles created do not show

I don’t know which WP version I’m using. I selected one but I’m sure it’s not, so please tell me WHERE can I see that.

My site http://www.medicoslideres.com has hundreds of articles which have been showing for nearly a year with no problem, but someone did “something” (who knows what) and as a result we cannot see the articles, we cannot see the videos, we cannot see the Tips which are in the main menu.

It is important to say that all of the articles are in NEWS MANAGER, they ARE there, you can edit them and do whatever. I created a new article today just to see if it could be seen in the correspondent category and, it did appear in the HOME (http://medicoslideres.com/) as the “last article published”, but it did not show in the page which handles the correspondent category, where it had to show.

Nothing can be seen except for some small examples that a person tried to fix at http://medicoslideres.com/articulos-de-cirugia-plastica-y-estetica-todos/, but in this latter instance there’s no option to go to the second, third, fourth and so on pages, since there are about 200 articles in that specific category, and you can only see the first page, no the rest.

Can anyone help me PLEASE solve this situation?

Thank you in advance for whatever you can do to help me.

Jose