Android Question [ Game Server Ask ] what is the most effective ?

There are entire books devoted to your question, I don't think you're going to get a simple answer from the forum.

The answer for you will vary greatly depending on how you're going to implement communication, how many concurrent users you expect to have, and a host of other variables that only you can answer and have not provided to us in your post.

I can say that, generally, a timer to fire events for updating your "local copy" of the information is not a good answer. I would investigate MQTT and have your server broadcast notification that your clients may subscribe to. There are many other ways of doing this, of course, but assuming a simple "mmo game" model this would probably be the quickest/easiest to implement.

Just my two cents

already managed to solve some doubts about pool connection, now I'm more relaxed! but I still have a question about it ... can I make several NonQuery Insert at the same time in mysql?

I tend to use MSSql, but it looks like you can: https://www.mysqltutorial.org/mysql-insert-multiple-rows/