Thank you for your help Maybellyne. I appreciate it very much.
I am stuck with a theme builder called Bricks. When I activate Yoast it changes all the page titles and Meta descriptions (ad i have tried to change them in Yoast, and it does not work. Since I have a minimal understanding on how Bricks operates I made my posts by simply using the WordPress blocks builder, but I have no way of adding a meta description. That is why I only want Yoast to be active for my posts.