A wish for changing an accidental setting that's now become permanent

Hi everyone. 

I've accidently clicked on some settings in word that have become a permanent default now.
It's resulted in all tables showing up with a bold top line in all new documents too (see attached file 2), athough that isn't how it looks in the doc it happened in. In there a funny sequencial structure happened showing like this:
1 textline,
"return",
1 single table with a repeating content that doesn't show up with a bold top line
"return"
1 or more single tables showing an undesired bold top line. 
(see attached file 2)

This pattern continues over and over again through the full alphabet in the document. 

I've tried fiddling with all the obvious settings to undo it, but unsuccessfully. Had help from a "geeky" friend too, as I am no tech savvy. Also unsuccessfully.

I don't remember what I clicked on, just that two clicks happened very fast and that I thought I was in the word document right next to the one it happened in, meaning I had 2 windows open at the same time. My eye caught two settings switching, and there I was with this that's now an unwanted default one. 

Anyone here who have any idea what I've clicked on or how to get back to the original Word settings? 

Hope someone can help or knows how I can get help resolving this. 
Thank you in advance. 

/Nanna