I was stupid and I cleared the default for my general gallery on my phone (not the google gallery but the other gallery) now there's no option to change it back, how do I change it back to default? It's on my Galaxy J7 Perx.
Welcome to Android Central! So did you set your Google Photos app to be the default gallery app instead? If so, go to Settings>Apps, select Google Photos, tap Defaults, and clear the default. The next time you want to open an image, it should then ask you which app to complete the action. Make sure you select your stock Gallery app.