Sorry, I didn't notice someone actually posted! Thanks.
Well ENTJ is a possibility, sure.
As for your points:
1. Well, I can think things out on my own too. Yes I do keep up certain mental activity longer if I talk to others. But if it's about problem solving, I'm better off thinking on my own, well I can ask others for ideas, but otherwise it would just get in the way talking to others.
2. No, I don't gather much information on stuff before doing it. Where did you get that impression? I usually just start and figure out things later. I do feel like I'm starting "from nothing" but it's okay.
3. Yeah if I'm motivated. Is ISTP not good at this?
4. Same. Is ISTP never goal oriented?
5. I do have an inner world, but yes, the outer world as well, hmmm, this I or E question is actually pretty hard for me :/
What do you think? For you, was it obvious you were an introvert?
ISTPs can be motivated but it's almost a requirement for ENTJs to be.
Yea it's obvious I'm an introvert. I have talked to some ENTJs that say they come close to looking like introverts since they spend a lot of time alone. Try and figure out if you use Ti or Te. Te usually uses seemingly objective information in the world. Stuff that is popular and accepted. Ti uses it's own logic and can ignore popular and accepted ways of doing things. It's much more independent and contained.
Oh and I like planning for concrete things, like, plan a day out with tasks needing to be sorted
Sounds ENTJ. ISTPs and ESTPs aren't really big planners. More of improvisers.
Yes, I easily nitpick, criticize arguments and theories, I get really anti-social doing this. Rude, arrogant, whatnot. Yes, I do like seeing things inside the framework of the right system.
This sounds more like Te needing logic to work in the external world. Ti doesn't need to change other people's opinions. So yea I would bet on ENTJ.