Your plant is a Peperomia obtusifolia. It does not have a disease, but it does have a root problem. I'm not sure what caused it to deteriorate initially, but the repotting has definitely aggravated the problem. The pot is too large for the root system and the soil quality does not look sufficiently porous.
I don't know what you mean by a "place with no direct sunlight," but I suspect you have it too far from the nearest window and that may have been the reason it originally started to decline. Keep it close enough to a window that it gets a couple of hours of direct sunlight each day and bright indirect for the rest of the day.
You may be able to salvage it potted as it is if you improve the light and water it very carefully, but that will be difficult.
The alternative is also dicey. That would be for you to carefully undo the repotting you did by gently removing the soil you added while trying to leave the soil in direct contact with the roots intact. Then move the roots and just enough soil to cover them into the SMALLEST pot that they will fit into snugly. Use a porous potting mix with added perlite for porosity. The smaller pot and more porous potting soil will help it dry out more regularly so the roots no longer suffocate.
If you discover there are few healthy roots remaining, then take tip cuttings from each stem and root them together in water or a small pot filled with a porous potting mix.
