I have a MacBook Pro (15-inch, 2.53GHz, Mid 2009),
is it true that the newest OS X version that it can be updated to is El Capitan version 10.11.6 ?
Yes. It's true. El Capitan is as far as it can go.
It is true.
Starting with the page on 10.12, you can look at the header of that page and go to the next higher system to find which Macs are compatible with which system that are newer. Except for M1 Macs, you should be able to use the migration assistant to a newer Mac with the right cables and hardware fairly easily to get your documents over. Catalina begins 64 bit compatibility, which most of your applications probably are not.
What's the latest OS X version I can update to my Mid 2009 MacBook Pro?
