I have two issues that are probably related. The first issue is that the wi-fi network does not connect automatically when starting the Ubuntu-Mate. The second issue is that the time and date are desynchronized with the Internet time and date. To be synchronized, I will need a connection to the net.
My question is, how to automatically connect to the web with my wi-fi network?
Thank you Steven. I have the latest version of Ubuntu but I found the solution to the problem. Now, my Wi-Fi works well (without the Ethernet connection). The date and time are now synchronized with the Internet.