When the player buys/sells items, it is recorded in the settings file and the console :)

I really need this feature 🙂 pls

There are already tickets for keeping track of all trades and for printing notifications, which seems to be what you are suggesting:

• #354
• #598

Edit: Follow-up ticket to keep track of the 'log to server console' request: #750
Logging to a file is already covered with the CSV trade logs.