impress modifying slides LibreOffice 7.0

Dear LibreOffice community,
I try to modify single slides in Impress, as I do not want to have the same layout for all master slides. I tried with the following tutorials indicated below. I am using LibreOffice 7.0 OS is Windows.
What is the role of the view normal button? Is that the slide to be modified? Then after clicking apply to selected slides by choosing another template style nothing changes. What is the best way to control each slide individually? Sigh.

https://elearn.ellak.gr/mod/page/view.php?id=2744

If you want to have different slides designs, you must also use different masters.

Please have a look at this description to see if it helps you:

My Master Slide in Impress

Meine Masterfolie in Impress – LibreOffice 7.0 (German/Deutsch)

My Presentation in Impress

Meine Präsentation in Impress - LibreOffice 7.0 (German/Deutsch)

If you have then any questions, please contact here again.

Good luck!