Can I create an online room in which people join and enter the room with a code, and so on like online games, or not?
Yes. You should be able to do that with Thunkable.
I am an Arab
I do not understand what you just said
Yes, you can do that. There are chat apps and tutorials that can help you with it.
I mean, I can create a game and enter, for example, individuals in different rooms!
If possible, can you give me a video link or something?
Start by Googling chat room Thunkable.
See this link.
I do not want to create a chat application, but a game that will enter, for example, 5 people in the same room playing the same game together
You will use a similar process to get 5 people into an online room to play a game as you would for a chat app.
Study the chat app and adapt it for your game.