The background of the problem is similar to this question but the question is different. Is this plagiarism or something similar in a master's project?
As my work is of expository nature and 2 of the 5 papers which I have studied give background and motivation and even comparison of the methods used by them in other papers in beginning of the paper ( it is given as section 1 of the paper called "Introduction"). Example -> Image
So, in my rough draft of thesis I wrote about 65-70% of the lines written in this picture in not necessarily same grammatical language because the authors have given really nice explanation and background which I thought to be worth adding. Obviously, mathematical terms can't be different from that of authors in any line which I wrote.
Keeping in mind that I am doing expository work as my thesis doesn't prove any new result (I am giving detailed proofs of all the results which have only been outlined, in fact there were a lot of such proofs) and will cite the original papers in preface and others in reference, am I committing plagiarism by writing part of this "introduction" in my masters thesis where I will explain the proofs of lemma and theorem in the papers?
Any help will be deeply appreciated!!