Bumping this up, hoping you get a reply from someone more knowledgeable than I.

I usually repot newly purchased plants believing growers use a mix just to sustain the plant through sale. Since you have it double potted, when you water make sure it drains thoroughly before placing it back into the outer part. After watering I allow the Plant to sit on a stack of newspapers a few hours to wick out excess water before placing it inside the outer pot. I’m not sure how much light this plant needs, so you might Research that.I think it’s a Dieffenbachia

In the near future, it would be best to remove the main pot from the cache pot when you water; then, after the soil is fairly close to dry but not wilted, water thoroughly so the entire soil mass is soaked and 15-25% of the pot's volume has exited the drain hole. It looks like there are holes through the plant's pot bottom at the sidewalls (that's good); so, after watering, tip the pot at a 45* angle with a drain hole down (lowest point of the pot). You can prop it in the sink until it stops draining. This will 'force' quite a bit of any excess water from the pot, water that 'wants' to remain in the soil. You can see by the images below how much difference this can make insofar as water retention is concerned by comparing tipped B to upright A. The shaded area represents the fraction of the soil that is 100% saturated (not good). How much excess (perched) water any given soil will hold depends on several factors, but is primarily driven by the size of the particles from which the soil is made.

I think it would be better to get the plant straightened out before you repot, but after the plant has recovered, a plan to repot into a soil that allows you to water appropriately without having to use work-arounds or worry about soggy soil ruining root function/health would be very helpful. Focusing on root health by managing the plant's water needs is a critical part of root health, but rather easy if you make it your focus. I'll leave you something about using a "tell", which you can use to "tell" you when it's appropriate to water. That, along with making sure you're supplementing nutritional needs, providing adequate light/temperature levels, should get your plant turned around.

This might be helpful, too.

Using a 'tell'

Over-watering saps vitality and is one of the most
common plant assassins, so learning to avoid it is worth the small
effort. Plants make and store their own energy source –
photosynthate - (sugar/glucose). Functioning roots need energy to
drive their metabolic processes, and in order to get it, they use
oxygen to burn (oxidize) their food. From this, we can see that
terrestrial plants need air (oxygen) in the soil to drive root
function. Many off-the-shelf soils hold too much water and not enough
air to support good root health, which is a prerequisite to a healthy
plant. Watering in small sips leads to a build-up of dissolved solids
(salts) in the soil, which limits a plant's ability to absorb water –
so watering in sips simply moves us to the other horn of a dilemma.
It creates another problem that requires resolution. Better, would be
to simply adopt a soil that drains well enough to allow watering to
beyond the saturation point, so we're flushing the soil of
accumulating dissolved solids whenever we water; this, w/o the plant
being forced to pay a tax in the form of reduced vitality, due to
prolong periods of soil saturation. Sometimes, though, that's not a
course we can immediately steer, which makes controlling how often we
water a very important factor.

In many cases, we can judge whether or not a
planting needs watering by hefting the pot. This is especially true
if the pot is made from light material, like plastic, but doesn't
work (as) well when the pot is made from heavier material, like clay,
or when the size/weight of the pot precludes grabbing it with one
hand to judge its weight and gauge the need for water.

Fingers stuck an inch or two into the soil work ok
for shallow pots, but not for deep pots. Deep pots might have 3 or
more inches of soil that feels totally dry, while the lower several
inches of the soil is 100% saturated. Obviously, the lack of oxygen
in the root zone situation can wreak havoc with root health and
cause the loss of a very notable measure of your plant's potential.
Inexpensive watering meters don't even measure moisture levels, they
measure electrical conductivity. Clean the tip and insert it into a
cup of distilled water and witness the fact it reads 'DRY'.

One of the most reliable methods of checking a
planting's need for water is using a 'tell'. You can use a bamboo
skewer in a pinch, but a wooden dowel rod of about 5/16” (75-85mm)
would work better. They usually come 48” (120cm) long and can
usually be cut in half and serve as a pair. Sharpen all 4 ends in a
pencil sharpener and slightly blunt the tip so it's about the
diameter of the head on a straight pin. Push the wooden tell deep
into the soil. Don't worry, it won't harm the root system. If the
plant is quite root-bound, you might need to try several places until
you find one where you can push it all the way to the pot's bottom.
Leave it a few seconds, then withdraw it and inspect the tip for
moisture. For most plantings, withhold water until the tell comes out
dry or nearly so. If you see signs of wilting, adjust the interval
between waterings so drought stress isn't a recurring issue.

Al