about "되지만"...
I hope everyone who wants to learn Korean knows this - one of hard things in Korean is to know about verb-change. It would be very difficult for beginners even for advanced learners.
so... I try to expalin it simple and clear as much as I can.
as George wrote, its meaning depends on its context.
However, 90% we use this "되지만", one is allowed but the other is not.
basically, "되지만" comes from two words, "되다": become & "하지만": but, however.
meaning, "that(this) is ok but not this(that)".
for example, 너는 되지만 나는 안돼. you could(can) do it but I couldn't(can't).
이것은 되지만 저것은 안돼 - this is ok but not that one.
먹어도 되지만 웃는것은 안돼 - it's ok to eat but not to smile.
so on...
There will be exceptions and more usuges. but, Korean learners keep it simple!
If you want to know two things once, you might lose both.
It's better to catch it one by one and keep it simple.
More importantly you will learn the difference eventually.
Language does not have rule since people create rules.
The best way to learning new language is to enjoy it. make a lot of mistakes and learn it from the mistakes... don't be afraid of making mistakes... the more mistakes you would make at the beginning, the more chance you would not create the mistake in real life. cheeers, cheeeerrrrrs....