grab
The German word 'greifen' is a verb that translates to 'grab' in English. It is used to describe the action of taking something with your hand. For example, 'Er greift nach dem Buch.' means 'He grabs the book.' Please note that in German, the verb 'greifen' is conjugated according to the subject and tense, just like in English.
I have to reach for the bag.
In this context, 'greifen' is used to describe the action of reaching for something, in this case a bag. The structure of the sentence is straightforward. 'Ich' (I) 'muss' (must) 'nach der Tasche' (for the bag) 'greifen' (reach).
They quickly grasp the concept.
In this case, 'greifen' is used in the context of mentally grasping or understanding something. This is a commonly used metaphor in both English and German, where the physical action of grabbing something is used to describe comprehension.
He was just able to grab the branch.
Here, 'greifen' is used to describe the action of physically grabbing something, in this case a branch. The phrase 'gerade noch' is used to describe a narrow escape or in the nick of time.