Hello!
No i did not find a solultion. Someone from the forum did take a look. You can view the code of the theme (webshop > 3 dots beside theme name > edit code) in there are files with translations (locale), but the sentences we are looking for are not there.
I think those lines are baked into the Shopify code, which we can not change.
I hope someone from Shopify reads this and makes the return reasons editable.