How can I open the control centre?

This is normal behaviour .

Do you clearly see the Control Centre pull down when you do this?

You are not supposed to leave the Control Centre pull down always/constsntly shown.

Tap anywhere on your iPad's scrren ( away from the Control Centre pull down ) to hide/dismiss this Control Centre pull down menu.

Your iPad’s screen should return to its normal clarity.

It's Michel.

Try a hard reset of your iPad by holding down both the Home and sleep/wake buttons simultaneously until your iPad goes to black and restarts with Apple logo, then release the buttons.

Good Luck!`

What year and model iPad do you have/own?

The “A” model number can be found on aluminium back of your iPad in small print right under the larger bold print “iPad”.