Do you think teaching making things dificult and slow can be profitable for someone?
Do you think it's mandatory to sign up for a course to learn a language?
Rafael, if you have had a teacher that has made things difficult for you on purpose in order to make money out of you, you have been swindled.
As to whether it is mandatory to sign up for a course, it depends on the learner. Do you need someone to push you all the way or are you able to study (a lot) on your own?
As a language teacher, I find this topic interesting. I don't think too many teachers would deliberately make the learning process longer to make their students pay more. It's not good for them if the students tell everyone they know that the teacher just takes their money away, so they may realize pretty soon that no new students come any more. But anyway, if a student stops coming after passing a language exam, moving abroad or for whatever reason, more students come to take their places, so making the existing students come more often than necessary makes no sense. And I would never do that anyway. But the pace of learning depends on the student - it can't be too fast, otherwise they won't learn the material properly. So in certain cases, it's better to progress slowly, when the student can learn everything properly, while others learn a lot on their own, so we can progress really fast.
As for the need for courses, it depends on the student again. I learn languages easily, so I learnt Spanish and French by myself, from a book and TV, but I also started learning German by watching films. People who find it hard to learn a language usually need to go to a course or a private teacher. But I think the best way to practise a language is by language exchange between friends.
As for people who said you would never learn English on your own, I already told you that you proved them wrong a long time ago... You speak & write English really well. I hope they see it too. It's amazing that you could learn English so well in just two years. So all hats off, it's a fantastic result.
Language partners aren't teachers. You can chat and learn naturally with native speakers here as an exchange just by being friends. You can talk with others right here Francisco if you are studying on your own.
Rafael, even if you learn from a teacher, it is you who has to work hard to learn a language. So in learning a language your contribution perhaps counts more than that of a teacher. You can also try to find a language partner who wants to learn Spanish from you and can teach you English in return.
There are negative people everywhere, in every field, in every country... and there are positive ones too! Best to concentrate on the positive ones generally if you can.
Apparently, you have proved the nay-sayers wrong because your English writing is beautiful.