Why I started to be interested in learning English

I always thought learning English was very tedious and very boring. I always thought it was impossible to master English.

When I met three international students last year who speak English as fluently as native speakers although English is their second language , (to avoid a sentence fragment, you could add after a comma : I changed my mind.)

They looked very confident and bright.

They taught me how much they enjoy studying English and how thieeir language skills chnaanged thieeir lives.

After that, I started to enjoy learning English. I am still not able to express my opinions clearly. However, I do enjoy doing this (or: trying).

My dream is to speak English fluently so i I can make a lot of new frends all over the world and have dialogues with them! (suggested change, as 'have dialogues' sounds a little formal and static, you could say, 'and communicate with them')

Hello Masa!  Really nice work here, your English is quite good, very minor issues : in English we say 'i before e except after c - but we should add of course, except in the case of their and...' Do keep writing and communicating, it's the best way to improve.  Best of luck with your goals!