There are some Urdu words for "speechless": 1) la jawab hona/karna: us ne mujhe lajwab kar diya: He made me speechless ( I could not find any argument). be sukhan: usually used in poetry. raat ki be sukhan khamoshi men (in the speechless silence of the night) alfaz na hona: mere pass alfaz nahin keh men aap ka shukriya ada kar sakoon (I don't have words to express my gratitude towards you) But I think there is no suitable expression in Urdu for "to be speechless with joy". Your sentence could be translated like that (with some improvisation) woh apni khushi ka alfaaz men izhaar na kar saka (He could not express his joy with words). woh itna khush huwa keh keh us ke pass alfaaz na rahe.

Speechless : Urdu meaning : Khushi sey pagal hoona. " when he saw the present she had brought, he became speechless" Apney doost key toohfey ko deekh tey hi who " khushi sey pagal ho gya"