[deep]

System 5°major diamond 4°

---

Now South what to bid better? Ty at all for help me.
I think 5♦ or Double

[gszes]

you would never be embarassed to lay this dummy down in 5d but you might be embarassed huge if you X 4s and it makes
If p has a singleton spade and wishes to go to 6 you should have excellent play If p is void in spades and wants
to consider 7 you should have excellent play. X here essentially says we have little potential at 5 level lets defend.
X is more for a hand with two aces and out and no big fit for p. You are too strong and your dia fit is too large
for X:))))

[dake50]

Revamp Key-ask to 14/02/3wo/3w
and 5D signsoff when it should.
I actually play 4Nt in compressed auctions
as general slam ask - here needing S-control.

[whereagles]

Dbl. By a mile. Pard is favourite to have a balanced 12-14, in which case you'd have to be quite lucky to make 5♦.

4♠ is very likely to go down 1-2, maybe 3. Take the money.