Center post titles

Hello there ?? ..

I am setting up a website for my client, but i got some troubles with a few things.

Here is the website:
https://www.lindenskov.net/

Here is the CSS:
https://lindenskov.net/wp-content/themes/SimplePress/style.css

First of all, i would like to center all my post titles.

Second, i want my logo to be placed a bit higher.

the last thing i got some trouble with is the wallpaper.
How do i make it properly?

[please don’t bump after such a short time]