We can imagine the foreign exchange market as a market. If foreign currency wants to enter China, it will be converted into local currency in this market. Everyone has changed, which makes the local currency scarce, so it becomes more expensive and appreciates. In order to curb this situation, we will throw away the local currency, increase the supply of local currency, and reduce the scarcity above, so that the appreciation of local currency will be controlled. Then how do you sell your local currency in the market? You just change your local currency into foreign currency, which means buying foreign currency. So the situation is just like what you said, "In order not to let the local currency appreciate, sell the local currency and buy foreign currency".

If the government holds foreign currency, it can't spend it in its own country, that is to say, foreign currency can't circulate in a large area in its own market, so its consumption capacity for domestic goods is not strong. When the government changed foreign currency into local currency, that is to say, the obstacles to the circulation between domestic currencies were removed, there were still so many commodities, but the number of local currencies increased, which led to inflation.

In order to make the local currency appreciate, foreign exchange can be exchanged for a large number of foreign materials hoarding, so that the currency ratio will increase, and inflation will be reduced or negative. But other countries are not stupid. We ordinary people know that we should sell foreign exchange, but will foreigners not understand? It won't make you run out of dollars easily and quickly. Spend whatever you want, and spend a lot of money on materials. There is another way to stabilize the currency. On the premise of stable domestic productivity, the central bank will recover the local currency and maintain the proportion of commodity currency after the local currency is converted, so there will be no inflation, but do you think the government will? Just like burning money. The last method is to develop and solve the productive forces. In short, the depreciation of the local currency is definitely directly related to domestic productivity and the value of the issuing currency, which means that the currency circulation exceeding GDP will definitely lead to inflation.