I have changed and rephrased some of your sentences. I have also noticed that you have a tendency to choose complicated words in your text. Due to this, you increase your vulnerability of making mistakes.
Keep in mind that making mistakes is perfectly acceptable during the learning process. I make a lot of them and I don’t blame myself.
Read my suggestions.
(The method of languages education vary a lot of the person to person.)
The method of learning a foreign language can vary a lot from person to person.
For me, the traditional method of learning a language is ( that it) an incredible waste of time.
Another possibility: For me, the traditional method of learning a foreign language it’s an incredibly wasteful way. Or if you want to be even more dramatic: it’s a colossally wasteful amount of time.
If I (wouldn't ) wasn’t learning English on (not by) my own
(on my own is a fixed expression) I wouldn't be capable of (to) communicating.
Capable is an adjective that is always followed by the preposition of.
When I'm in class I learn a considerable number of new words, complicated grammar questions and rules. (don’t use just here. You described a lot of information – if you want to say that you received massive amounts of information and that can be undeniably distracting rephrase or sentence.)
(You don’t have many new words…. You learn many new words….)
(When – let’s avoid repetition for the
richness of English’s vocabulary)
On the other hand, while I'm studying alone (avoid repetition of the verb learn) I pick the subject and I learn through the topics that I like. Another advantage of individual study is ( that it allows for) repetition.
In class, students are always whining about repetition. (the verb whine in this context is most used in the participle form) (Although it is not wrong : Students who whine about their grades…) .
We get bored easily because we don’t have a (passive- choice of word) receptive mindset from the start.
Or: we don’t start with a positive mindset….
But when I’m studying (as an individual) alone, I can repeat the same content as often as I want or need to.
Of course, studying alone it’s( become) harder to clear up our doubts. Maybe the best way for learners who are eager to learn is (to have) doing a course and learn many things alone as a whole.