To begin with the good sides, 18-year-olds form a more relevant public opinion by voting at this age. I don't get the meaning of this sentence.
Good sides are the advantages. "Relevant" can mean anything. It probably means the 18-year-olds enable a broader cross-section of the population to be represented.
Furthermore, voting, which is a kind of
acivil obligation, stimulates a serious implementation in social events. Should we put an a between is and kind? Yes, but the underlined expression is odd
Although one could be immature at 18, voting leads him/her to crucially important contemplation that he/she is the one who, eventually, decides about the future of his country.
Contemplation seems inappropriate to me, I would replace it with thought or revelation for instance.
"Immature" should be changed to "not mature enough". Contemplation which means to consider something carefully and deeply works for me.
We all have witnessed fine examples of those (the 18-year-olds?) who had changed their political attitudes
becomingand became more aware of political happenings. which, also,refer to them. We have all witnessed; the end of the sentence is odd
On the other hand, opposers to this theory emphasise that 18-year-olds are simply not capable of being rational about voting. Isn't opposers of the right construction? Opposers, the people who oppose, is fine.
According to various psychological studies, people are,approximately, far more mature at their twenties. In their twenties. "Approximately" does not fit.
In spite of this, these parties may come out (turn out?) to be the wrong ones because of their incapability to act (deliver) as promised, while the more rational adults will (would) choose serious parties, rather than 18-year-olds. Unnecessary comma (parties rather)
Taught by personal example (From my personal experience), my modest opinion is that the aging vote(voting age) should be moved (raised) to 21 because the main mission of the young is to develop the country by studying and hard-working habits (working hard) while the adults are there to elect. Apart from not agreeing with the conclusion , two things stick out to me: "Taught by my ? personal example", and what does aging vote mean?
not a teacher
Student or Learner