"Yes, you're welcome."
My understanding is that each addresses a different usage of welcome in English, and High Valyrian handles them differently. In English, we say "Welcome" as a greeting. Jiōrna is used to do the same in Valyrian. For instance,
Jiōrna, Daenerys! Kesy ñuhon lenton issa. "Welcome, Daenerys! This is my home."
In English we also say "you're welcome" as a response to being thanked. Valyrian doesn't appear to have that meaning/role for the word jiōrna. Instead, Valyrians say biarvose.
Kirimvose, Tyrios! Kesy ēngenkor averilla issa! "Thank you, Tyrion! This is tasty wine!"
Biarvose! "You're welcome"
Biarvose is technically the instrumental form of biarves:
n. 4sol. happiness, jubilation, luck, fortune ( < biare + -ves.)
The instrumental case, which you'll learn about later, is generally translated as "with," or with the sense of "by means of." So in this case, biarvose would translate literally to something like "with happiness."