I need somebody's help to understand these meaning。。。。。
1.The camera goes back and forth a few times in a sped-up shot to him doing
this and turning a the lock on the safe.

what does" forth a few times "mean?

2.(taking the baggie, studying it) Get
a rush on the prints. (He hands it back
to her.)
what does"Get a rush on the prints."mean?

3.Lawrence in his white
doctor‘s coat along with three blue-scrub
clad medical students.
what's the meaning of"blue-scrub clad "?

Question

I need somebody's help to understand these meaning。。。。。
1.The camera goes back and forth a few times in a sped-up shot to him doing
this and turning a the lock on the safe.

what does" forth a few times "mean?

2.(taking the baggie, studying it) Get
a rush on the prints. (He hands it back
to her.)
what does"Get a rush on the prints."mean?

3.Lawrence in his white
doctor‘s coat along with three blue-scrub
clad medical students.
what's the meaning of"blue-scrub clad "?

Answer

The first two responses explain "back and forth" well.

2. "Get a rush on the prints" refers to the fingerprints on the baggie. It means to hurry up and compare the fingerprints to the fingerprints in the criminal database to see if there's a match.

3. Doctors and other medical staff often wear blue uniforms called scrubs. The medical students are clad (wearing) blue scrubs. 
These are scrubs: http://www.lifewearproducts.com/images/categories/PandaScrubs.jpg

Answer

The term "back and forth" means to advance and then return to the same point or location with frequency or continuous actiivity..  Example:  The couple went back and forth for almost an hour before they decided to end the debate;  The pendulum on the clock went back and forth as I fell asleep from watching it.

Scrub-clad  means that one is dressed in this type uniform(scrubs) that is worn by surgeons and some hospital staff.

Answer

1. back and forth (It moves backward and forward or from side to side) a few times (more than once)

2. Get a rush on the prints (hurry up and get it done)

3. blue-scrub (scrubs are outfits worn by surgeons and other surgical staff) clad (clothed)

Answer

： } 
you·ve made a little mistake, "goes back and forth" ，it`s means “来回、往返”