The writing in steemit and also the reading has improved more my writing skills than the speaking ones. About speaking ones i believe that watching movies or tv shows with subtitles in english helps me a lot, but that only works for people that already have a medium level of english. Another thing that i found here on steemit, its everytime i read some word i don't know the meaning, i look it up in online dictionary or google translate and it helps me grow my english vocabulary ;)