I love italki, keep going it up!

"Keep it up!" is probably a better translation of 加油！in this scenario

I knew know about this website from a man who makes videos whose named "fulinfang(拂菻坊) Fang Fulin". In one of his videos, he told us that this website could help you to correct your articles .He used to be helped by some friends here. So I tried to write an article in on italki. Without one day  Without delay(?)/Soon enough, there were two people to who corrected my article and gave me some advice about learning English. I'm so appreciate appreciative for their favor of their helpfulness. Also,some people would encouraged me in on italki. Definitely thankful for their support. No matter how difficult it is, I will certainly continue learning English! I love italki!

"Knew" is past tense but you, right now, do know about this site, so you should use "know".

Saying "I know this website from a man" makes me think you know this guy in person, so the second sentence feels weird. Providing additional information to say "from a guy who makes videos" or maybe "from a youtuber" or a "youkuer" makes the second sentence sound more natural.

当我们说中国朋友的名字，总是会在句尾加上他们的性。比如说我有个朋友，他叫张瀚林，但是讲英语的时候就会叫 "Hanlin Zhang"