1. He has never visited Ha Long Bay before.
`->` This is the first time + S + have/has + Vpp = S + have/has + never + Vpp + before.
2. She has worked here since last year.
`->` S + started + to V/ Ving + thời gian = S + have/has + Vpp + since + mốc thời gian
3. We have eaten lunch since it started to rain.
`->` S + began + to V/ Ving + when + S2 + V2/ed = S + have/has + Vpp + since + S2 + V2/ed
4. I haven't had my hair cut since she left me.
`->` S + last + V2/ed + when + S2 + V2/ed = S + have/has + Vpp + since + S + V2/ed
5. He hasn't met me for 5 months.
`->` The last time + S + V2/ed + was + thời gian + ago = S + have/has + not + Vpp + for + khoảng thời gian
6. We haven't met ... for a long time.
`->` It + be + khoảng thời gian + since + S + last + V2/ed = S + have/has + not + Vpp + for + khoảng thời gian
