Formating issue in twenty forteen

Hi,

I have wordpress running with twenty fourteen theme and have set
text to one column. I wanted to increase textwidth and finally got it done by modifiying style.css as.:
.page-content {
margin: 0 auto;
max-width: 80%;

However, There are 2 remaining issues:
When there is text with pictures, pictures are too far to the right.
In the editor distance between text and picture is much smaller.
See https://www.cyclingeurasia.com/ueber-uns/

And-the text editor is still as narrow as it was before and therefore doesn’t show the same formating/spacing as the final static page.
I tried to change this by modifying editor-style.css as follows:

for the Body:
max-width: 720px

but it didn’t change anything.

Any ideas how to get rid of both problems, I tried several good guesses but they didn’t work so far. Thanks in advance!