You can learn a lot from online courses. Maybe you can start working on your own project. Doing real-life stuff is often more complicated that learning the same thing in school. (Okay, it depends on what you want to learn. My hobby is computer programming, so there are thousands of books and tutorials available.)

Too bad the high school is a waste of time, but you only have to do it once in your life. Is there an option to skip a grade? That would save you a whole year of time, and simultaneously provide a greater challenge (learning the two-years worth of school knowledge in one year).

Please make sure you get that high school diploma, even if it requires switching schools or doing advanced/short courses or whatever options are available in your country. Ask your teachers if they can give you harder assignments so you stay interested, or give yourself harder assignments. But whatever you do, get that diploma. Your life will be much easier that way.

i don't know why but every time i was getting closer to a girl i felt the desire to never talk to her again

Use some psychologist to find out; the information may be important. Meanwhile, here are some random guesses:

• getting closer to a girl is very stressful, so at some moment you just want to have less stress in your life;
• initially you lower your expectations, because getting "any girlfriend" seems like the priority, but once you have a realistic chance, you realize that you actually do have expectations, and she does not meet them;
• you are actually gay or asexual, and you only want a girlfriend because of social pressure;
• you are scared of intimacy or sex, so you stop the process when the danger becomes too real.

The advice will be different depending on the real course. For example, if you are a gay or asexual, I would say "stop pushing yourself to do something you actually don't want to do"; if you are scared of intimacy, I would suggest a therapy; if you have too high expectations, I would remind you that dating is not a lifetime contract, and you can also have fun and sex with someone whom you plan to replace later (this may sound evil, but it's what many people do).

For the annals of "Today i learned About Myself"

During my 3 years of highschool, i really wished a girlfriend because i was feeling lonely all the time and it was very difficult for me... So i began to look for a girlfrien and i noticed that many girls wanted to date me and i don't know why but every time i was getting closer to a girl i felt the desire to never talk to her again... It's very weird and i can't explain it it's a very new experience for me and that's probably why i'm fleeing.

For the annals of "Today I Learned About Myself":

I just noticed a pattern in every job I've had. I get upset and bored at my job when there's no one left in the office that I can learn from. Every time I reached that moment, my gut urged me to switch jobs. I connected the dots and discovered that pattern because I'm feeling that again.