If you are viewing a non-default rendition then up in the top right you will see a blue dot (next to the Sie, language or orientation).
If you then change a setting in the selection properties (for example, X value) you will then also see a blue dot next to the X value setting indicating that the position has changed in this rendition only.
To reset (in this case) the X setting, right -click the blue dot next to the X setting and choose 'remove value for rendition'. There are also options to copy and move the value which is what I meant by 'or look at other options'.
I also saw that PubCoder offer training - if you're able to it might be worth investing in getting a few hours training if you're struggling especially since I've only just seen this (and unfortunately this forum doesn't seem to generate notifications when people respond to your posts).