Your first is OK.
The second needs work.
Many new models of S martphone have been put on the market.
The price of the iPhone 5s should be marked down for selling.
Interested in Language
Are both sentence correct?
Am I using the phrases correctly?
Or, if not, please advise me, thanks for help!
During the class in English lesson, teacher was writing the key point on the board.
And then, students are writing down the notes for reference.
Many new models smartphone put onto the market.
The iPhone 5s should be mark down the price for selling.
Since your first two sentences happen at the same almost the same point in time, I'd keep the same verb tense in both of them - either change 'was writing' to 'is writing', or change 'are writing' to 'were writing'.
It's confusing to refer to sequential events in two different tenses.
Wear short sleeves! Support your right to bare arms!
***** NOT A TEACHER *****
I would personally be more comfortable with something like:
"During the English lesson, the teacher wrote down the key points on the board, and the students then copied them for reference." (I am describing what happened yesterday during the English lesson.)
If you wanted to use the progressive, then I would suggest something like:
"When the earthquake hit the city, the teacher was writing the key points on the board during the English lesson, and the students were copying them for reference. The teacher and the students quickly got under the desks for safety."