Future Simple or going to

I think I will do it tomorrow.

I think I'm going do it tomorrow.

Mark is going to work harder next tern.

Mark will work harder next tern.

They probably won't open a new sports centre in our town.

They probably aren't going to open a new sports centre in our town.

The sky is grey and it going to rain.

The sky is grey and it will rain.

I hope I won't get another baseball cap for my birthday.I've already got five!

I hope I'not going to get another baseball cap for my birthday.I've already got five!

There's nothing in the frige. I'll go shopping.

There's nothing in the frige. I'm going to go shopping.

We like hot summer so we won't spend our hoisdays in Scotland.

We like hot summer so we aren't going to spend our hoisdays in Scotland.