These are great questions from Arminius1871's Journal.
Questions I love to ponder.
I'm working on a Science fiction story about a colony of Europeans who establish,
"New World" called New Prussia.
That Exo Planet and stars had a radiation shield that protected its solar system. That shield failed, and that planet was claimed by the Europeans. The planet is slightly larger than earth.
Most of the of the original emigrants were Anti Earth globalists. So when an Exo Planet was found, those Globalists were more than happy to be rid of the "old world traditionalists".
When do you think, humans will colonize the first planets and the moon in our solar system?
Can we terra form Mars and Venus (and others?) and how long will it take?
Yes, Science could create those possibilities. terra-forming Mars might be easier to imagine. Each exo planet will be it's own experiment to terra-form. Some may be easier than others.
How will life be for example on Mars, what effect has the low gravity, can they do sth against it?
All off worlds will have different changes to whatever Earth life forms reside there. Going from zero gravity in deep space to low gravity of Mars will seem normal to the space traveler.
When will we be able to reach exoplanets and other solar systems?
From what we know, not likely. But, hopefully soon.
Which technologies will we need and have in which century?
I believe that technology is being designed.
Will artificial intelligence come and boost our technology exponentially so we will those sci-fi tech much earlier than expected?
Yes. I believe the early forms of AI is being designed at the present time.
Will humans survive until then?
Oh yes. Europe and the planet might look different. Humanity and traditions will still be here.
How would the society be on exoplanet colonies? Will they create their own new nations?
Yes. Their own world governments and maybe Kingdoms. Earth globalists will have their problems with these new "free" people. Something like the early kingdoms had, as they colonized the "new world'. I believe modern people will have better insights as they establish exoplanet colony's.