Are theme changes lost at update?

Hi,
Since new versions of grav and the themes are rolling out quite frequently I wanted to as if changes done to the themes (like changing the images, the width of certain elements, etc.) lost after updating the site? If no: great! If yes: is there a way to prevent that from happening?

You can use a theme child (name get from wordpress for you can understand easy) explain more in this blog post: http://getgrav.org/blog/theme-development-with-inheritance
If you have more questions you can reply here :)

Thanks namaless! I'll do a bit of reading then ;)

You are welcome :D