First of all thanks for the examples.
We can see that you have made an effort to explain your goals.
Unfortunately, at least for me, the explanations are confusing, so I don’t really understand what you want to do.
Obviously, like me, English is not your first language, so I would recommend that you use an Online Translator to help you.
Please note, the better/precise the question in your mother tongue is set, the better the translation will be.
To the questions:
Use the find dialog, go to the Mark Tab and mark the hits, optionally set bookmarks for each line
Probably a regex search for \(.+?\) could provide this.
How do you know if a sentence begins or ends. For this you actually need an AI that was really programmed for it and even this one won’t work 100%
and 5. I do not understand.
Translated with www.DeepL.com/Translator (free version)