ᐅ Mold Infestation in Carport Karibu - Classic

Hello everyone,

Almost a year ago, we built a carport from Karibu. Everything went well during assembly. Unfortunately, now the carport has severe mold growth on two sides, and I would like to know what I can do about it.

I never painted the carport because Karibu says that pressure-treated wood does not require painting.
Can I sand it down, and if so, what should I use? After sanding, should I then paint the carport? If yes, with what?

Thanks for any help.
Best regards