Q: Some macbook's fans don't work?

To check, you can run an Apple Hardware Test:

https://support.apple.com/en-us/HT201257

Note that an error free AHT is not conclusive.

Also some temperature/fan speed applications will indicate if a fan is malfunctioning.

If you have any doubts, make an appointment at an Apple store genius bar for a FREE evaluation.

Ciao.

In the interim, install a temperature/fanspeed application and see what information that generates.

If you have a pentalobe driver, you can take off the bottom plate and make a visual inspection of the fans.

Ciao.

The output that you posted indicates that you have a 13" 2015 MBP which according to iFixit.com has only one fan.  The major concern is that the fan is NOT functioning.

Your best option is an appointment at an Apple store genius bar for a FREE evaluation.  Fan replacements are an easy repair and should not deplete your bank account.

Ciao.