Someone asked this question yesterday. Here's the answer I gave:
'Get' on its own, as a main verb, has three basic meanings:
1. Become ---> It got dark/She got fat/We got tired
2. Obtain ---> I got this as a birthday present/ I went shopping and got some milk
3. Arrive ---> I got home late/ The parcel got here on Friday
This third meaning is the basis of many verb+preposition or verb+adverb combinations, for or example, get up, get down, get through, get over, get out, get in, and so on.
In some cases, the meaning is very clear and literal. For example:
Get up = rise
Get down = descend
Get out = exit
Get in = enter
In other cases, such as 'I'll get around to doing it soon', the meaning is more idiomatic, and you have to learn the meaning of the phrase as a whole.
'Get' can also be used as an auxiliary verb:
In the passive voice ----> He got killed = He was killed
In causatives ---> I got him to help = I persuaded him/arranged for him to help
I hope that helps.