Oooshhh... I had no idea you didn't know how to save the data in a DB. Explains a lot.
Okay...an important question: After the user has completed all 150 pages, do you need to continue to remember all the answers from all pages? (I would kind of assume so, else why collect the answers in the first place, but...)
There are several simplistic approaches, but whether they match your needs I can't tell.
Simplest of all:
CREATE TABLE questions(
PRIMARY KEY( pageNumber, questionNumber )
CREATE TABLE users(
userid INT AUTO_INCREMENT PRIMARY KEY,
CREATE TABLE userAnswers(
CONSTRAINT FOREIGN KEY userid REFERENCES users(userid),
CONSTRAINT FOREIGN KEY (pageNumber, questionNumber)
REFERENCES questions(pageNumber, questionNumber)
That says: Every page gets a page number (could of course be a page name if you preferred). Every question on each page gets a question number.
Every user has an id. When they login, you lookup that id by username and password. (If not found, they can't log in.) When found, you store the userid in a session variable. THAT IS THE ONLY DEPENDENCE on cookies you have: The userid stored in a session variable, on the server.
When they answer the questions on a page, you add all their answers to the answer table. Each answer is identified by the userid along with, of course, its page number and question number.
Simple as that.
At *ANY* time, you can go look in the database to see what answer *IF ANY* the current user has given to any question.
So if they were in the middle of answering questions on page 73 and needed to stop for the day, they hit the SAVE button. You save all their answers on that page. (You might also save their current page number in a separate table, so that they don't have to remember it.)
Tomorrow, they login. They ask for page 73 (or you remember that's where they left off), you bring it up, but in the process you fill in all the answers they had already made yesterday.
What could be simpler?
It's not terribly sophisticated, because it doesn't allow for questions with multiple answers, for example. And there are many other improvements possible. But it's an easy starting point.