I'm going to assume that you're talking about the days of the British empire, in advance of the Opium Wars.
A. Britain was losing money because they were importing more than exporting.
In Britain, there was a strong market and high demand for imports from China like silk and porcelain. But the British did not have enough items of demand or silver to trade with China. So the British, wanting imperial dominance, began a process of importing opium into China -- a drug which became a high demand product. The Chinese government under the Qing dynasty strongly opposed the opium trade, and the Opium Wars were the result.
On a present-day note, in January 2018, Britain's prime minister Theresa May announced intentions to increase trade with China. As of the beginning of this year, just 3% of Britain's exports were going to China and just 7% of Britain's imports coming from China. Don't expect any wars over this. Prime Minister May and a number of Britain's business leaders went to China to work on negotiating trade deals.