1. I will drink tea this afternoon because since noon I didn't drink tea.
2. They will stay in Beijing for three days and return home on Friday.
I'll drink tea in the afternoon, I won't drink tea at noon
he's been in Beijing for 3 days, he'll return on friday
side note, I don't understand the use of "qián" here
前qián means “before” ，structure is “time+before”。
1. I drink tea in the afternoon, I don't drink tea before 12 in the afternoon.
2. He lived in Beijing for 3 days, he comes back home on Friday.
1. In the afternoon I drink tea, before 12 noon I do not drink tea.
2. He is going to stay in Beijing for 3 days, returning home on Friday.
1) I drink tea in the afternoon, but not before 12 o'clock.
2) He is living in Beijing for three days, on Friday he returns home.