Question about Child theme

First of all, I apologize for my poor English 🙂

I use a theme for our site that needs a lot of changes.

I was told to use Child theme, So that the changes we have made will not be lost in the next update.
To make changes to the Child theme, for example, when I want to change the RTL file, I have to copy the RTL file from the main theme to the Child theme folder and make the changes to that file.
But my problem is that if in the next version of the theme changes are made in the original RTL file of the theme, then the contents of my RTL file that I copied in Child theme are old and those new changes are no longer applied and I have to bring the new RTL file and re-apply my changes again.

So what is the practical use of using a Child theme? Now, what is the difference between changing the RTL file directly or bringing it to the Child theme folder and then changing it?

Is it possible to load the CSS or PHP or even Java files I want to change into Child theme and then write only the code I want instead of copying the original file and that Edit?

• This topic was modified 2 years, 9 months ago by Jan Dembowski. Reason: Moved to Fixing WordPress, this is not an Developing with WordPress topic