F1 Visa extension

[pk123]

Hi all,
I am a current phd student - my 5 year F1 visa is expiring this december, and I have scheduled visa interview seeking F1 visa extension for additional 1 year.( I have to travel in december to attend annual ceremony of my close family member who expired last december )
My questions :
1)My phd advisor would like me to come back in 3 weeks, hence I have planned trip for 3 weeks. How can I make sure that they will grant me visa without causing too much delays ? Can I prepare any documents in advance/ in a better way so as to make the process efficient - I am asking because I heard that sometimes people get stuck because of background check etc..
2)Has anybody here done this kind of F-1 visa extension within same degree.. ? Could you please tell me what kind of questions to expect during the interview...
3)If they ask why I need more time - should I go into the technical details of my work or can I simply say in brief words ?? I am really worried about this one, as I have no clue what is expected of us ..

Can somebody please respond to this - as I saw some other posters in similar situation but no replies as yet..

If anyone here had a similar situation - could you share your visa experience.. how long did the processing take for you,..


Thanks a lot,
pk123

[kabkaba]

Unfortunately, there is no way to predict or prevent that from happening.