WILL IS USED .
To express a future decision on intention made at the moment of speaking.

Examples:
It`s Jane`s bierthaday." "It is? I´ll buy her some flowers."
I`ll give you my phone number.

ERROR

When we want to talk about future facts or things we believe to be true about the future, we use
'will'.

• The President will serve for four years.
• The boss won't be very happy.
• I'm sure you'll like her.
• I'm certain he'll do a good job.

If we are not so certain about the future, we use 'will' with expressions such as 'probably', 'possibly', 'I think', 'I hope'.

• I hope you'll visit me in my home one day.
• She'll probably be a great success.
• I'll possibly come but I may not get back in time.
• I think we'll get on well.

If you are making a future prediction based on evidence in the present situation, use 'going to'.

• Not a cloud in the sky. It's going to be another warm day.
• Look at the queue. We're not going to get in for hours.
• The traffic is terrible. We're going to miss our flight.
• Be careful! You're going to spill your coffee.

to express an offer.
I`ll carry your suitcase.
We`ll wash the dishes.