Battery holds charge for about one or two hours only

My battery's charge on my MacBook Pro 13 2020 with 16GB memory, 2 TB flash storage and a 2 GHz Intel Core i5 runs out of battery when unplugged in a bit over an hour, two hours at best.

I have tried turning off Bluetooth, and everything else I could think off that could be running in the background (I changed the display setting), and keeping only the programs I am using running. Usually, that would be Firefox and Word. Occasionally, I still leave mail running, so I will get notifications. At most, when needed, I keep preview on, if I need to consult a document while working.

But even when I have only the browser on, and perhaps word, the charge will come down to less than 15% too quickly, gaining speed as it goes below 50%.

In systems preferences, the battery is reported as being in good health.

I have recently tried keeping the laptop plugged, except when I definitely need to move around, to no avail.

I used to leave the computer on, and only rarely shut down. I have tried shutting it off when not in use, and found no difference.

When I travel, I can't use it to work during a flight, due to the short short duration of the battery charge.

Any suggestion?

Any recommendation whether in general it is better to leave it plugged continuously or unplug it as soon as it is charged?

Also is it best for the laptop that I shut it down every night, or only when necessary?

Thanks.