i discovered a rather individual problem, which is why I couldn't find a solution on the net or the forum search so far.
I am using a Google font called "Julius Sans One" for the blog title, tagline and the menu bar. It displays fine for all browsers for title and tagline, however, for the menu bar in safari the words are displayed dashed looking. Once I hovered over a word with the mouse, the font is displayed fine afterwards. This occurs only in safari, only in the menu bar.
I attached some screenshots to display the problem: