How can I credit to sources I'll use for my paid or free video tutorials on YouTube or Udemy? I don't remember that I saw sources section on Udemy tutorials or YouTube videos, whether they are a course or not. Even, on books such as,

https://www.unf.edu/~wkloster/2220/ppts/cprogramming_tutorial.pdf
https://cs.brown.edu/courses/cs173/2012/book/book.pdf
http://lug.cs.uic.edu/wiki/lib/exe/fetch.php?media=cybersecurity_for_dummies._palo_alto_networks_edition_by_miller_l.c._z-lib.org_.pdf

Nevertheless, I really care about plagiarism, ethics, copyright and any other rights of the people or companies and need help for following topic.

I am a computer engineer and I'll generate free or paid courses / videos in the informatics sector such as computer usage, programming, network administration, etc. on Udemy or YouTube.
These courses completely will be generated combination of the Turkish and English information on the web (to generate high quality courses) such as pdfs published by universities as above, videos, official websites (such as microsoft.com, apple.com, etc.), blogs, wikipedia, articles, etc. and will be published as Turkish.
I know that I can't add directly bulk texts, images, video parts from different sources, etc. However, I need to add similar things to them to explain a topic. And I know that I can't tell an article's result is my work, etc.
I plan to use a slider software for definitions section of the videos. However, I don't think every video will have this section. And I plan to tell what I understand from the sources with different words or sentences and add different examples as much as I can.
Does my plan considered as stealing, non-ethical, plagiarism or copyright or any other right issue in this case? Do I need to credit every word or sentence seperately? How can I do this in a video?
Or is it enough to add all of the links in bulk used to generate the course / video at the end of it? Do I need to specify author name, date, etc. of my sources as in academic paper? If yes, which standard should I follow?
The most general rule is that once you cite, you are no longer plagiarizing.  You can submit someone else's entire paper, and as long as you (very clearly) note that you didn't write a word of it, and that it was someone else's paper that you found interesting, you are no longer plagiarizing, as you are no longer representing someone else's work as your own.
The standards for citation are different in different settings.  In fully formal papers, you need to cite fact-by-fact, because every contribution needs to be traced directly.  In a video, it is sufficient to say that what you're presenting isn't developed by you, but really the work of other incredible people, and that you will link to those sources at the bottom of the video.  Again, the standard is whether you represent the work as your own or not.
A setting like an instructional video does not need (and typically does not support) each fact being separately cited.  Further, no one would expect it, any more than they would expect it in a lecture at university.
Good luck creating your course!