To 'get at' someone or 'have a go at' someone means to try to make that person change their mind about something, or their behaviour, by disagreeing strongly with their attitude or position.

'I'll get at him about what he has done.'

'I'd like to get at her for that, she should not have done it.'

'Whenever those two are together, he gets at her.'

It can also mean 'to get hold of' in a physical sense, or 'to get access to' something.

'That dog is trying to get at the bone.'

'He's trying to get at him so he can start a fight.'

'If he gets at her, he'll hit her.'

'He wants to get at his pension, so that he can retire [from work].'

To 'get round to' doing something means to find the time or resources to carry out a job or task; the implication is that it will not be right away, but at some time in the future.

'I'll get round to sorting out the house when I get back.'

'Will he ever get round to doing it ?'

'Tell me when they get round to clearing this stuff.'

Well, ''get at'' hast at least three meanings at my knowlege
  - get at somebody : means that you criticizing that person .
                Ex : The opposition can't stop getting at any proposal made by the president.
  - get at something : mean to reach or have access to it.
                Ex : The documents were classified as confidential, that's why I couldn't reach at them.
 - get at : can also mean to learn
                Ex : It's sometimes difficult to get at the truth.

About, get around, here is an example : My grandmother gets around with the help of a stick (She moves from one place to another)

I hope that was somehow helpful to you :)

*Could you give me some examples to help me understand the meaning of these phrasal verbs?

I'm not sure what you're getting at (I'm not sure what you're trying to say)

I'll try to to get around to it when I get the chance (I'll try to do it when I can)