You can learn a lot by allowing the camera in fully auto mode select its own settings and note what they were and how they look compared to your manual settings. See the differences and figure out why the camera exposed differently than you did. Use the internal flash which is effective at shorter distances, up to about 20 feet, and all these will be adjusted automatically by the camera for a good exposure. Then when you use manual modes, you will have a good idea of the range of various settings and anything you want to change for artistic reasons, compensate by changing another parameter to maintain the same exposure. For example if you take a photo of a person indoors of a person 10 feet away, depending on the ambient light levels, in fully Auto mode the flash will pop up and the shutter, aperture and ISO will all be auto adjusted to arrive at a good exposure. Artistically you might have other ideas of how it should look but note the settings the camera selected. These are a good starting point for your next, manual exposure. But if you wanted to get shallower depth of field of the person to blur the background a little, open the aperture 1 stop, and decrease the speed 1 stop...same exposure but with shallower depth of field, Say you have a fast lens and want more blur, open up the aperture another stop and slow the shutter by 1 stop..again same exposure but a lot less detail in the background. The flash is so fast that it freezes the subject so motion blur is not much of an issue until you get down to very slow shutter speeds, much slower than you could normally hand hold a photo without flash.
Now you have a base range of settings that work. If you keep the same settings and scene, add your manual flash after closing the popup flash. Set it to 1/4 power and take the same shot. Is it under or over exposed? If either, change the power to compensate. Now you know a good base combination for that shot. Do the same without the flash outdoors to get familiar with what ranges to expect for different conditions. Take a test shot fully auto and seen what settings it chooses in full auto. After doing this for a few days you will understand what values are good starting points for different conditions for manual settings. If there is decent light, keep ISO low in any of these tests. At ISO 400 or less, not noise should be seen in a well exposed image. In good light, even ISO 12,000 makes good low noise prints but when light is poor, it is a struggle for low noise when pixel peeping, on any camera ever made.
Photography is not about specs of cameras, it is light, and lack of it that controls the whole process. The biggest mistake beginners make is assuming that cameras should see as good or better in low than our eyes. They often do if the print is the same size and distance but you are seeing the details close up on a monitor you would never see in the same scene with your eyes. Noise in prints is seldom a problem because prints are seen at a normal intended viewing distance. A lower resolution camera often appears to have less noise when pixel peeped at 100%. It is not noisier and in fact is surely a lot better but 100% on a 6mpx camera is much less of an magnification factor than 100% on a D610 or D850. At 100% you are blowing up the high resolution image much larger so you are seeing a small smaller area of the image filling your monitor. So expect to see more noise even in noiseless images with high res images. All images have an intended viewing distance and size. The size of the image and distance are related. For art work and photos that distance is what the creator of the work intended, and in almost all cases the artist or photographer intended the viewer to be far enough away to see the entire frame without scanning back and forth with the eyes. The whole image taken in at once is the intended viewing size. A billboard looks terrible at 1 foot away and what is displayed might not even be recognizable because whatever you are seeing in color blobs are out of context to the actual scene. Get 50 feet away or more so you can see the entire image of the 20 foot billboard and it can look razor sharp. Same with art in an art gallery, large full wall paintings make little sense 4 feet away, but 20 feet away and the message is clear. Filling the screen with your photos shown in its entirety is how you intended people to see your work. Up close might not makes as much sense because they can only see parts of it. Your image is a whole and should be seen that way. That is why prints often get better response than monitors....because people zoom in and ruin the message. Pixel peeping is a bad habit to get into. If it looks noise free at normal viewing distance and size, what possible benefit would be found by seeing 20 times magnification revealed color blotches? The color blotches contribute to its message at 4 feet away on a 30 in monitor. The message is only conveyed at the intended viewing distance and size. That is a ratio so getting further back means the message is best seen as a larger display.
Good luck, you have a GREAT camera that pros 15 years ago would have killed for its capability in image quality. They would have gladly paid $50,000 for such a camera.