Plagiarism isn't just about copying words, it's about failing to credit sources, especially those contributing intellectually to some work.
Of course, I'll change sentence structures and words in my talking and tell in a different way as much as I can
You can't take something you've read and just reorganize the sentence structures and call it your own work. Even just copying paragraph structures and organization is plagiarism. You can, however, read something, then after understanding it, write about it in your own words, and credit the source as the place where your understanding originated.
As long as you write in your own words (different from changing sentence structure or using a thesaurus) and cite sources, you are not committing plagiarism. You can cite any source you can access, there's no limit on that (besides exceptions where something is provided to you in private under some sort of non-disclosure agreement, private information protected by law like health information, or censored by a government for national security reasons, etc).
Copyright is a legal issue, and especially if you are planning to profit off some venture you need legal advice beyond what you can get asking questions on StackExchange. You will run into copyright issues if you copy bulk text (even if you cite it and make the original source clear, if you copy "too much" a citation isn't sufficient; where this line is depends on jurisdiction and ultimately what is decided in a courtroom) or reuse images in a way inconsistent with the license those images are provided under.
