C. We use I'll (= I will) when we decide to do something at the time of speaking. (e.g. Oh, I've left the door open. I'll go and shut it.) We cannot use the present simple (I do/ I go etc.): I'll go and shut the door. (not I go and shut)
a. We often use I think I'll ~ and I don't think I'll ~ (e.g. I feel a bit hungry. I think I'll have something to eat.)
b. In spoken English the negative of will is usually won't (= will not) (e.g. I can see you're busy, so I won't stay long.)
C1. Do not use will to talk about what you have already decided or arranged to do. (e.g. Are you working tomorrow? (not Will you work)
a. Generally we use will to talk about the future, but sometimes we use will to talk about now. (e.g. Don't phone Ann now. She'll be busy. (= she'll be busy now))
C2. We often use will:
a. Offering to do something (e.g. That bag looks heavy. I'll help you with it. (not I help))
b. Agreeing to do something (e.g. A; Can you give Tim this book? B: Sure, I'll give it to him when I see him this afternoon.)
c. Promising to do something (e.g. Thanks for lending me the money. I'll pay you back on Friday.)
d. Asking somebody to do something (will you~?) (e.g. Will you please turn the stereo down? I'm trying to concentrate.)
e. We can use won't to say that somebody refuses to do something. (e.g. I've tried to give her advice, but she won't listen.)
Idiom 365
Every cloud has a silver lining: Be optimistic, every difficult or unpleasant situation has some advantage
Example: Don't be unhappy that you are failing your interview. You will see, every cloud has a silver lining.