Short Sale process and time line question

[Jason Kramer]

This is my first short sale and there is a lot of information regarding short sales on bigger pockets and lot of other sites but i am even more confused after reading the articles and trying to compare what stage of the short sale process i am in.

I submitted an offer on Short sale through my agent.  after 2 weeks  of going back and forth the chapter 7 trustee signed the purchase agreement. now My agent says  it is in the short sale investor approval stage. and it is a waiting game till the Bankruptcy court approves the short sale.

almost all the articles i read says it takes months for the bank to approve the offer , in one of the  email communications  the sellers agent  that  "the trustee is recommanding the bank to accept the offer" and we should get the response in a day or two. 

couple days later , the Trustee signed the purchase contract.  does this mean the Bank approved the short sale ?  

can any one help me understand what a "short sale investor approval" is . The sellers agent said it can take upto 120 days.   is it really going to take that long or 120 days is the max time line? 

also  are short sale investor approval and Bankruptcy court approving the short sale the same ?

TIA