This stems from visiting a stunning garden last week and coming away with some nice shots but nothing jawdropping.
Plenty of people can make lovely images with a phone. But a phone is harder to get "jawdropping" images from since the depth of field is so wide (you can't make a "blurry background" unless you use the computational power of portrait mode), and of course the sensor is small.
But, that said, outdoors in good light, your phone should be adequate for your needs. I hesitate to recommend a "photography" class because most of the things you would learn there would only be applicable for someone using a camera with manual controls. Some apps will let you do that on the phone, but not quite to the same extent as on a big camera.
I would suggest you learn about composition, lighting (and not adding in extra light, but how to use the available light well), etc. Things that are external to the device you are using for photo taking and that would apply to any photo you want to take. There are quite a few tutorials on the site I linked above that can make a big difference for you if you take the time to read them.