I have a question about a young fig that is growing very nice. If you see the picture, this fig developed a second trunk. In this stage of growing, it's better to remove the second trunk and only keep the main trunk?
I was thinking that maybe the second trunk will take away some energy and slow the growing process.
What do you think guys, should I removed it or it doesn't affect at all?

It's personal preference.  I'd keep it, many others would eliminate it.  A lot depends on how you want your trees to look  and if there's ant practical rason that branch would be in the way.  Every time a plant puts out a leaf it gets more energy from the leaf than it used to produce it so it is growth, it doesn't interfere with growth.  Whether it's growth in the way you want it to grow is a question only you can answer.  :)

If you want a lot of branches why cut the first one that shows up?  Air layer it at the length you want to keep it when the time comes.

You have also been presented a perfect opportunity for an air layer

Air layer sounds good!! I didn't think about that posibility