Hi there,
Using a plugin like Autoptimize is a good first step: https://generatepress.com/fastest-wordpress-theme/
As for your images, you’ll want to:
1. Run them through some sort of optimization. A service like this can be helpful: https://imagecompressor.com/
2. Make sure the image size isn’t way larger than what it’s displaying at. For example, if an image is within a 500px wide area, the image should be 500-1000px wide (no larger).
Let me know if you need more info 🙂