CSS automaticly changes overnight

Hi guys
I’m a bit off a rookie in this sport, and therefore probably i’m a little stuck
When i use the onepager in wordpress it does perfectly fine what i want.
But there are a few things that i cannot modify in the plug-in editor online on the site.
so i figured out in my inexperienced opinion that i am looking for “onepager.build117.css”.
That is what firebug told me anyway, and indeed offline i toke that file to dreamweaver and gave it the edit that made the changes the way i like ‘m.
After finish i uploaded the file back to the server again and overwrite the old file .
Then everything looks perfect and just as i want it.
But when i take a look at my site the next day it is back to the settings only made in the plug-in editor itself and not the fine-tuning in dreamweaver.
So several font types and link colors for instance are changed, and radius 0% goes back to 100% in testimonials for instance.
and i find on the server new files like: “onepager.build142.css, onepager.build145.css, onepager.build148.css and same files with .js extension” and also my edited onepager.build117.css is completely revered to the file before the manually modified data in dreamweaver.
I never made the new files, so that happens automatically.
Maybe there is an easy way to turn it off or something like that, but i don’t know how to do that.
Would it be possible if any kind soul looks in to this a help me out please?
Thanks a bunch in advance

Daan

https://wordpress.org/plugins/tx-onepager/