In order for someone to help you with API Request questions, it is critical that you post here the API Request you are using.
Remember to replace your Key with [THE_KEY] , or something like that.

For example, if you are using the parameter & sort_by = popularity.desc,
the answer may be different because the popularity changes every day.
For this and other reasons it is necessary to see your API Request.

i use this API https://api.themoviedb.org/3/discover/movie?api_key=[THE_KEY]&language=en-US&sort_by=popularity.desc&include_adult=false&include_video=false&page=1

So, this is the reason.
Popularity changes all the time.
If I'm not mistaken, it is calculated based on:

• Amount of access to the website page
• Number of accesses by API
• Quantity of inclusion in Lists
• Number of votes
• Average votes
• Etc... Etc... Etc...

Alias, see the first row of Posters on the TMDb homepage.
It is the Most Popular row.
Every time I update, the order changes.

some values are optionals and sometimes comes without being optionals

What I didn't understand is what you mean by Optional Values.
What Values are you talking about?
In the answer, all the films have the same items.
An item may be blank because no user has added the data.