Replace fan with Dell-part and you should be good-to-go.

Seek-out pro-help (ie, qualified technician) if you need a little help.
Backup your vital files, shut-down, and unplug-from-wall, before opening its case.

power on, hammer f2

then read BIOS logs to see WHAT fan fails.  CPU , or case. fan.

the alert is real. (if coin cell not bad)

• the fan is packed in lint.
• the fan cable fell off or lose
• the fan runs too slow,  due to bad bearings, not lint.
• the fan is dead.
• a cable lands near fan and block blades of said fan..  move cable tie it back.
• RPM is is too low or on 4+ wire fans too high, (too high is PWM Failures, inside fan mostly)

only LOOKING first works. look at the fan even see it spin, does it?

or RTC coin cell battery is dead (mine was weak on my 3020 ) and NVram goes nuts, even fans can go nuts,

the battery is a first things first thing over 5 years old. my battery was 7 years, old and near 2.8v too low.