My mom was my 1st and 2nd grade teacher (admittedly a great one) and I feel like this helped me understand how my native language works pretty fast, as she'd motivate me to study and thoroughly help me out whenever I needed/wanted to. I was also into reading books so that helped me advance my vocabulary a lot. Now, as an adult, I believe I speak the language better than the average person in my age range but I may be lacking in more advanced vocabulary.

As far as English goes, I started learning at the age of 7 (we typically start learning it in third grade) but it was hideous as I could barely understand or memorize anything. The thing that helped me tremendously was listening to music, reading the lyrics and translating them into Greek. Also, I think the fact my mother tongue is Greek helped me learn English vocab faster/easier to be honest. Moreover, I started talking with a bunch of people whose native language is English during my early teen years which helped me advance a lot. My English is still nowhere near perfect but I'd like to think I'm fairly good at it haha

Reading books, watching movies/series with English subtitles and communicating with native speakers are all great ways to improve your skills in English