>>>I downloaded Open Office from the official Google site
This is the only site that you should have downloaded Apache Open Office from:
https://www.openoffice.org/
Like millions of others, I've downloaded it several times without any problems.
This site is reputable. (i.e. it doesn't get you to install software which will cause more problems than what it is that you're seeking to get rid of):
http://malwaretips.com/blogs/feven-1-8-ads-removal/
However it often goes for 'overkill' when suggesting how to get rid of problems. I'd actually start with Step %, which might well work on its own.
i.e. I'd download, install and run the free version of Malwarebytes Anti-Malware, which might cure the problem on its own:
https://www.malwarebytes.org/free/
Points to note:
1. When installing that program, take care to deselect the option to install a trial version of the full ('PRO') version.
2. When running it, use the 'quick scan' option (Which will still probably take over half an hour).
3. When you get to the end, click the button to show the detailed results, and then click on the option to remove everything found.