Site hacked? Links to other URL’s

I saw that links to a different URL when opening the page. I tried many things and found out that it’s was caused by 1 plugin. I deleted this one and the problem of redirecting the homepage was solved.

But now the problem still is that when I navigate to a subsite it still happens.

Can somebody tell me what to do? I’ve already (after Googling) this:
– Replace wp-includes and wp-admin
– deactivate plugins
– search in index, header, footer and so on for special codes

But I’m stuck now. Somebody with a tip?

The page I need help with: [log in to see the link]