Zuki font changes

Hi Marc, Ellen and everybody! I need some support  for changing CSS code. I use cyrillic and default fonts should have some aggustments which I can not realise using general fonts plugins…

  1. I want to change a font of all posts content from Libre Baskerwille to Karla, in this way the paragraphes and post content will be in the same style. Also it should be changed not only in blog posts pages but also on my front static page and in the area of all post in widget of static page sitebar. Could you please give me an additional code or code to change?
  2. Is it possible to remove “written by” on singe post below name of paragraph via CSS?

Thank you for your help beforhand! Viele Grussen!
Anna