A photo straight from a phone is often 3 to 8 MB. That is too big for many e-mail and upload forms, and it slows pages down. These are the ways to shrink it.
The quickest win is re-saving the image with efficient compression. JPG and WebP usually shrink by 30 to 70 percent with no difference you can see. Use the compressor and keep the same format.
Photos are smallest as JPG or WebP. Screenshots, logos and graphics with flat colors are better as PNG or WebP. Converting a photo to PNG makes it larger, not smaller.
A 4000 pixel wide photo is far more than a web page or an e-mail needs. Reducing the dimensions cuts the size sharply on top of compression.
Metadata adds a little weight and can include your location. GeoWipe strips it; the compressor also drops it when it re-encodes the image.