Purchases happen through the Webflow Marketplace. If you want a refund, you should contact their team.
You need to double click the whole element first, then double click again on the specific element that you want to change. You can find more info in this video.
No, there isn't any documentation.
However, changing the colors and text is like any word processor you may be familiar with. Elements too can be copied and pasted as you normally do with text.
In case you may need further, Webflow offers extensive tutorials on Youtube and a supportive forum community.
We don't offer this service, but can assure you that is really easy to do. For more info, consult FAQ n.2 and n.3
Yes, you can remove unwanted elements with ease, just select it with your cursor, then click "delete" as you would on any word processor.
You can rearrange the elements by simply dragging them on the screen. In that, Webflow is similar to Canva.
If you want to copy an element, just click Command + C (Mac) or Ctrl + C (Windows) as you would on any word processor.