Please, check my sentences in Chinese Mandarin (普通话)

Could you, please, correct my sentences? Thank you in advance!

1) I also learn a bit of coding.
我也学一点编码。
2) I have been to China, Greece and Spain.
我去过 中国, 希腊和西班牙。
3) If I need to work in the office, then I would prefer London.
如果我必须在办公室工作，那我更情愿是伦敦。
4) What is the average annual salary in Beijing?
在北京一年的平均工资是多少？
5) Have you ever thought about starting your own company?
你有没有想过创办自己的公司？
6) Now, we are testing the market.
现在，我们正在测试市场。
7）I chose 3D printers because I used to work in a 3D printing startup. So, I know the industry very well.
我选择了3D打印机，因为我过去工作在一个3D打印公司。 因此我知道该行业很好。