What do you want to offer me?

Ne bana sunmak istiyor musun?

Thanks a lot in advance.

Bana ne önermek istersin ?

But translate for daily usage; Bana, ne önerirsin ?

thanks a lot harpoon, still long way to know something from Turkish....

You are welcome, dont worry about it. You can solve easily

thanks, this is nice from you, but I do not think so......

If it help you, im still mixing up meaning of some English Idioms sometimes. I think, it is normal for foreign language. 

please coul dyou explain to me when you use istiyor musun? and when istersin?

I think you meant "ister misin ?"

Simply no difference. I think the examples will help you.

Do you want to go out ?

Dışarı çıkmak istiyor musun ? 

Would you like to go out ?

Dışarı çıkmak ister misin ?

You need the question particle MI in the sentence when there is no other question word there. In harp00n´s sentence

                                Bana ne önermek istersin?

there is one.

Thanks, now I understand....