Conditional Clauses

I have no idea what the first one means.

I've never read the second one, but it seems to be saying that you can get value from something one way or the other, but not both at the same time. The more common expression is that you cannot have your cake and eat it too. Once you sell something (or eat it), it's gone and won't benefit you any longer.

you're an english native speaker,right? I'm a turkish native speaker but That i understand is

First one;If I will not keep a dog, I bark myself. (It's like "I don't have a dog I bark myself")

Second one;If you cannot sell the cow and sup the milk. (If you can't sell the cow, you take the milk by spooning up)

What you think?

Matthew.90I will not keep a dog and bark myself

I think you mean "Why keep a dog and bark yourself?". This link may help:
http://idioms.thefreedictionary.com/Why+keep+a+dog+and+bark+yourself%3F

I've never heard that expression before in my life.

what you think for second one?

there is any your comment with it?

In my first response, I told you my thoughts on the second one.

You replied to my answer with apparent scorn.

I've never heard the expression "You cannot sell the cow and sup the milk" before, but Grammar Geek's explanation sounds right.