Hi Johann,
Hm, it seems like your current template is declaring any <h2> tag with <a> tag within to always hidden by default. The code can be found from the /templates/softtailor-folgeseite/css/template.css at line 970:
#siteContentBox_wrapper h2 a {
display: none;
}
As a temporary fix, I've enforce the title to always show by using css inside your /components/com_easyblog/themes/nickel/blog/latest/default.main.php . It is better if you can consult with your template provider regarding on the css code above so that it will not affecting other components that using <h2> tags and <a> tags.
Hope these help.