Your English is clear enough. These are great question. They are big questions so my answers won't be wholly complete.

You can't gain fluid IQ points, whatever your top processing speed is for recognizing patterns is what your top processing speed is. You can optimize it though, as in you can keep healthy and such. If you don't stay healthy then your fluid IQ will drop.

Your concrete IQ is different, as in the specific information that you know. That can increase well into old age. There is evidence that your brain and mind can keep gaining complexity into your 70s.

There is only so much info that your brain can process and hold, but it's impossible to know what that is over a lifetime. The way that we abstract information to create concepts by eliminating specifics allows us to hold many little ideas inside of larger ideas. This data compression ability is basically limitless, but you also lose data doing it.

I have more articles that just aren't written yet on the subject. I wrote about an idea called Jeff's Hammer today. More will be coming. http://www.jeffreyalexandermartin.com/2019/02/jeffs-hammer-conceptual-tool.html