We use Will for the future(tomorrow,next week etc.)
-Tomorrow she'll be in Rome.(Завтра она будет в Риме)
-Next week she'll be in Tokyo.(На следующей неделе она будет в Токио.)
I'll = I will / she'll / you'll ...
I won't = I will not / you won't / she won't..
We don't use will for things we have arranged or decided to do.
- We're going to the cinema on Saturday. (not ''we will go')
- I'm not working tomorrow.(not '' I won't work).
We often say I think I'll//I don't think I'll when we decide to do smth.
-It's a nice day.I think I'll sit in the garden.
-It's raining.I don't think I'll go out.
