be going to + infinitive:future plans and intentions o predictions / present continuous ( be + verb +-ing) : future arrangements / will o shall + inf. : promise, offers, and suggestions.
Present perfect: have/has + participable: past experiences, recent past actions , past exp. When don't say exactly when thet happened.
Present perfect + for/since : non-actions verb / Present perfect continuous: have / has been + verb +ing- ( action verbs)
Past simple / Past continuous: was/were + verb +-ing > Past perfect: had + past participle : (When John arrived, they went out)
first : if + present simple, will/won't + inf. :future situations
Second: If+ past simple, would/wouldn't + inf.: hypothetical present or future situation.
Third: If + past perfect (had studied), would + have + past participle: past
I like > She liked
I'm leaving tomorrow > He told he he was leaving the next day
I'll always love you > He said would always love me
I passed the exam>She told me she had passed the exam.
I've forgotten my keys > He said he had forgotten his keys
I can't She said she couldn't come
I may be late > He said he might be late
I must go >She said she had to go