i donot have bookstore in my apple books app

So to confirm, “Didn’t work” meaning you had one or two ore of those settings enabled and MDM profiles and could not shut them off, or you did not have any of those settings enabled or MDM profiles loaded?

One cause is Settings > Screen Time > Content & Privacy Restrictions > Click App & Feature Restrictions > Allow Book Store, but having Screen Time temporarily off should avoid that.

Are both your current location and your Apple Account set to a country or region where Apple is selling books?

Availability of Apple Media Services - Apple Support

Any add-on VPN apps installed?

Zoe2196 wrote:

I checked it already and found out that Apple Books is not available in my country.

do you know any other way to use the app?

You can use the app to read epub and pdf books you get from other places. For books from Amazon, you use the Kindle app, and other stores or libraries tell you what app is needed for their books

Zoe2196 wrote:

I checked it already and found out that Apple Books is not available in my country.

do you know any other way to use the app?

Among many fine sources, Project Gutenberg and the Internet Archive (text) have numerous ePub books available, and Internet Archive also runs the Open Library.

The DuckDuckGo search engine supports the inurl:epub keyword, which can help narrow searches for ePub files, too. Or search for inurl:pdf files.

Turn off whatever of Focus, Screen Time, and Parental Controls are enabled here, remove all add-on MDM profiles present, and check again.

Zoe2196 wrote:

Books app opens but I don’t have bookstore nor audiobooks

What country are you located in?