Several Problems after updating

Hello,

I need your help After updating I have following issues with my site:
– the content of the post is too narrow, whet can I make it larger?
– on the front page I always see the whole content of the posts, I want to see just a few first lines
– I can’t ajsut the sidebars- they are to big
– I can’t arrange the same font on all pages, I believe I put everyhnig black, but there are still apering letters in dark blue

I am not very familiar with css. Hope can arrange all the issues without it.