Learning Chinese and Korean

I went to Chinese school on the weekends for about 6-7 years and I stopped about 2-3 years ago, but I still remember how to read and write a lot of the characters. Speaking is easy for me since I speak Cantonese at home. On the other hand, I tried learning Korean online by myself and only finished the alphabet before I gave up. I just found that all three languages are pretty similar since some words/phrases sound the same. Especially in Japanese, if you know some Chinese characters, you can sometimes get the gist of whatever you're seeing is about.