If there is a status - «Enable FileVault» and «FileVault function of the drive (drive name) is ensabled» then proceed to item 4
4. In the bottom left-hand corner, click on the lock icon
(e.g.)5. Enter the Macbook password to unlock and press the «Unlock» button
(e.g.)6. Click on the «turn off FileVault» button
(e.g.)7. in the popped up box click on the «Disable encryption» button
(e.g.)