Speaking is the most important skill and actually the only skill that is necessary.

You don't need working speed at all because when you can't take anymore work, you can simply change the language, and then all task requests from your boss will be all gone.

You don't need health at all because when you do any thing that cost your health, as long as your health is more than 0, you will be safe, so you just need to watch your health and do things once you have at least 1 life, you will always be safe.

You don't need challenge until you become a president of a company because challenge only provide you some quick money and higher promotion chance when you collect all ways to be fired. The quick money can be obtained by changing your system time and do part-time jobs repeatedly. The collection bonus will be not useful until you become a president anyway since one of the "fired collections" requires becoming a president.