Under most circumstances, it is better to keep quotations at a minimum level. Instead, we should paraphrase and acknowledge other writers for the ideas we are using in order to develop our own arguments.
The international universities have set 15% as a percentage of quotations. The student is not allowed to quote more than 5% from one source. It is important for the researcher to commit the ideas without changing or modifying them. In addition, he must respect the views of the researchers. Even if these views are not consistent with his personal views.
It depends on the journal and university regulations. Generally, should be less than 15%. If the quote is more than three lines, the researcher should get a copy right permission.