"you're English is the least of the problems here"
Totally agree, I can see why you wrote that. My English is much better than yours. Thanks!!! Not too bad after all. I use that disclaimer so that when people read my posts, they can take me seriously and don't think I don't know how to write in my own language. I sugest you to use some kind of disclaimer like that too.
You're is another way of writing two words: 'you are' (as in 'you're making a mistake'). Your is a single word, and shows possession of a thing (as in 'your paper has some mistakes'). If you can substitute the words you are then the correct choice is you're.