Kodak Porta 160 on Nikon FM2 50mm - so grainy photos. Help needed

Hi Guys,
I'm new to the forum. I explore a bit of analog photography in recent months and I do struggle. I have Nikon FM2 with a 50mm pancake lens (E Series) and I shot Kodak Porta 160.
The light was very good (e.g. 1st photo) but all pictures are very grainy. Is it possible that I really underexposed it? It's all strange in such a good light I had. I was wondering if it could be because of bad scanning or maybe a bad working meter?. Kodak Porta 160 is known to have a very fine grain. I was expecting much better quality.

Could someone help me? I'd be glad. Thanks a lot in advance.
Best regards,
Adam

So I don't shoot this and haven't shot film for a long time so you shouldn't take advise from me.
So it looks to me your exposure is off, also the first image you are shooting at 11am, shoot in the morning or evening.

This guy shoots this film, he to has noise in the shadows but his results are better. He states +1 on exposure compensation in his images.

This site seems to be experts with this film and you should take advise from someone who uses this. This is their suggestions..
Once you’ve loaded up your camera, we’ve got a couple of great tips for shooting it:

• Kodak Portra of all sorts is a negative film. Typically, it’s light hungry. Meter for the shadows on someone’s face if you’re using it
  for portraiture. Otherwise, it’s not a bad idea to give it up to a stop
  more of light. On your camera, use the +1 exposure compensation
  setting.
• The modern iteration of the Kodak Portra film was heavily designed for scanning. So it will translate into digital very
  well. Kodak Portra 800 wasn’t designed for scanning: it’s got a more
  classic look to it.
• Kodak Portra is balanced to Daylight. That means that in orange lighting, it’s going to look really, really orange.
  To get an idea beforehand, use it alongside a digital camera and set
  that camera’s white balance to Daylight.
• This film is mostly designed for the way it renders skin tones. If you’re photographing
  someone with darker skin tones, balance it out with a silver reflector.
• If you’re shooting outside, the best thing to do is use a translucent
  umbrella to deliver really soft, smooth light on your subject.

www.thephoblographer.com/2021/06/26/koda...buying-guide-review/

Visit the review where they offer advise. They think best results are used with flash in the studio and this film is tough in natural light..

In our review , we state:

This is still a great film for portrait photographers, but I believe it to be best in a
studio scenario. I say this because this is where you have the most
control over your lighting. Sure, natural light is nice, but it can also
be tough to work with because of how the sun moves. If you are working
with it in natural light, I recommend using a reflector that compliments
your subject’s skin tones very well.”