Q.Small leaves on my heart philodendron
The original plant I got had larger leaves and eventually they started to get smaller I think it was overwatered and developed rot. So I trim off the living part of the plant and places it in water. Will the leaves get bigger? Or is it just a tiny plant now?

Certified GKH Gardening Expert
They will, eventually, get bigger. This is usually a symptom of root damage, which can happen with rot or with transplanting.
If you plant in a somewhat larger container, then the roots will spread faster, and deeper which will cause the leaves to grow bigger.
I believe with proper care, this will come back to be a completely healthy and normal plant.
This article will give you more information on the care of these: https://www.gardeningknowhow.com/houseplants/philodendron/caring-for-philodendrons.htm