Hi Ghazal
In isolation we use this phrase to invite/ask another person to do something and/or to take responsibility for doing something.
For example:
Person A: I have been trying to fix this computer for hours but I can't understand what is wrong!
Person B: I know a bit about computers. Would you like me to try?
Person A: Absolutely. Over to you.
It can also form part of a longer sentence. And in this case it usually means the same as 'to you' - the word 'over' is sort of redundant.
For example:
Person A: Hi. Do you have the documents that you promised to send me?
Person B; Oh sorry, I forgot to send them. I will send them over to you immediately.
Hope this helps
Chris