What's your question? Ask

It is hard to tell if this is insect related or white mildew related, but luckily both can benefit from similar treatment. Neem oil will take care of either of these problems. There are many other ways to treat either of these as well.

Here is a link to more information: https://www.gardeningknowhow.com/special/organic/natural-home-pesticides-organic-garden-pest-control.htm

I can't see the soil well, but it looks very compact. This would hold more water than these will tolerate. They will grow in, just about, anything else. Potting soil, with very little fertilizer in it will be best, as long as you only water it when it is almost completely dry.

This article will give you more information: https://www.gardeningknowhow.com/houseplants/pothos/pothos-plant-care.htm

A small percentage of mushrooms may be toxic to dogs, so it would be best to keep them from you pet.
Check with a vet to be safe.

The center of the plant may have died out from lack of light or even can be due to watering down the center of the plant.
This might be a time to propagate come new plants from the long tendrils.

https://www.gardeningknowhow.com/houseplants/philodendron/pruning-philodendron-plants.htm
https://www.gardeningknowhow.com/garden-how-to/propagation/propgen/adventitious-root-info.htm

I believe the plant is question is a pothos? Is this correct? There are a few reasons why it would lose leaves, or they can also become deformed instead. This article will help: https://www.gardeningknowhow.com/houseplants/pothos/poor-pothos-leaf-growth.htm

This is, simply, the water pushing out the air in the soil as it filters down to the bottom of the container. This will be more pronounced if there are no drain holes at the bottom, as the air will all have to escape out of the top. There is nothing to worry about here.

This article will help you with the care of pothos: https://www.gardeningknowhow.com/houseplants/pothos/pothos-plant-care.htm