What happens if I use the memory card of my phone in a Nikon D5200?

SD cards are generally interchangeable (with adapters). Their performance characteristics vary. The SD card class is a rating for writes, and the minimum requirements depend on the application.

For video, the write speed is of great importance and higher resolutions require higher write speeds.

In normal photography, writing speed tends to be less critical. Modern cameras have a buffer and can record a reasonable number of shots in burst mode. The aspect ratio affects the number of shots the buffer should take: fewer RAW images, more JPEG images. The cases where the writing speed of the card is likely to matter are sequential photo series.

My advice is to try it out and see if it works in the situations where you usually take pictures … but maybe not if those situations are critical. On the other hand, a good high quality reserve card can justify the cost. Again, it's about the reasons for taking pictures.

Aperture – Change the depth of field of the Nikon D5200

Guess, but do you take the picture or just look at the viewfinder?

Because the camera does not stop until the f / 32 until the moment it takes the picture. Only the actual image result shows a greater depth of field.

Otherwise, the lens is always wide open in the view the viewfinder sees and shows, to give a brighter view. Then only the setting is preserved at the time of the picture.

I do not know your focal length or subject distance, but I think you should improve the depth of field from about 1 foot to about 6 feet (at f / 32).