Answered by Shaykh Faraz Rabbani
My question is what should i do if i am in the 3rd rakah of the sunnah of Zhuhr and the iqamah starts for the fard? Should i do the salams while i am standing or should i sit down for Tashahhud and then do the salams? If i have already done the ruku or sujud for the 3rd rakah then what do i do? If i decide to finish the Sunnah and i miss one rakah of fard then is it wrong?

Walaikum assalam wa rahmatullah,
It is permitted to complete the four rakats of the sunna in such a case, quickly, and then join the congregation.
Faraz Rabbani
إن كان في سنة الظهر فأقيمت سلم على رأس ركعتين وصحح جماعة من المشليخ أنه يتمها أربعا لأنها كصلاة واحدة
مراقي