Since nobody has answered about ground planes:
When you have a circuit board fabricated, it's usually 2 (or more) layers. For a 2-layer board, there can be traces on both sides of the board.
Actually, let's start with all the layers on a board.
——— top silkscreen (labels, component outlines)
——— top soldermask (layer that gives the brd color*)
——— top copper (copper tracks)
===== board (circuit board core**)
——— bottom copper
——— bottom soldermask
——— bottom silkscreen
* And prevents solder from sticking where it's not wanted. This layer is built automatically by the layout software.
** Usually fiberglass, but other materials are used too.
The top and bottom layers can be bridged together with vias, which are small holes with plated sides to connect a track through the board.
The fab house process is designed to make 2 layer boards. If you only put tracks on one side of the board, it will still be processed as a two layer board.
So you have the potential for copper on both sides of the board. Often, a ground plane is used on the bottom layer. The ground plane will connect all of the points that are common, usually to the negative power supply. This includes your negative power input terminal, a number of pins on the ESP32 module, and (probably) your sensor common terminal.
You can still use the bottom plane to route traces where you can't make connections on the top layer (where 2 traces must cross to get where you're going), and the layout software will provide clearance between any traces on the bottom layer and the ground plane.
The only thing you must be careful about – whatever traces you run in the bottom layer must allow all of the ground plane to be connected. You don't want floating islands not connected together.