Be sure to cite quotations correctly.

 Use quotation marks to show where the quotation begins and ends.

From article:
"Creating an overly complex system negates the purpose of the system itself."

PLAGIARISM/WRONG:
Creating a very complex system negates the purpose of the system.

CORRECT:
Creating a very "...complex system negates the purpose of the
system..." (author, date, page).

"Creating an overly complex system..." does not solve the problem (author, date, page).

BETTER (use a paraphrase) :
Developing a system that is too complex does not solve the problem and makes the system not useful (author, date, page).

Also see "avoiding plagiarism"