1.By all means
Can I come to your party on Friday?
Yes by all means.
2. Sounds good to me
I'm cooking fish with vegetables for dinner, is it okay with you ?
Sounds good to me.
3. Okey - Dokey
Let's meet up for lunch on Sunday.
Okey- dokey.
4. Why not ?
Let's go out for dinner today.
Yes, why not?