I am assuming that you mean "text books". I don't know what subject you are looking for, but there are two free options: creative commons books or books donated into the public domain by universities or individuals. An example of this is the open stax library

https://openstax.org

Your other option are books with expired copyrights. You can find some at

https://www.gutenberg.org, the haithi trust or archive.org, or by using the online books page search at pensylvania university.

But you must check that the work is in the public domain. You are fortunate because Algeria has a liberal copyright policy as a +50 country, and you might therefore also use some alternatives from either faded page in canada or gutenberg australia. Canada and Australia are 60+ countries.

But, I must mention that your options for creative commons humanties books that focus on those parts of the world that need free books in this genre are not that many. The open text humanities books i have seen have focused on european or american culture. In maths and sciences, however, there seem to be some good options.

You can also use academic search engines, like core.ac.uk or https://www.base-search.net in order to find "open access" publications, articles and dissertations. Some universities also have databases of freely accesable dissertations that may not have been indexed by core or base. (there are few other academic serches as well)

The library of alexandria has a huge website, and seems to do many things online? They might know about arabic alternatives?