I have been using GIMP now for 18 years.
Most things you can do in Photoshop you can do with GIMP (but for free!).
With this fully-fledged photo editor, you can create your own adverts for Facebook, images for your website and email campaigns.
Google search the many “Gimp Tutorials” on the internet to help you with your initial learning.
Once you learn layers, tools, selecting and editing techniques, then you can create just about anything.
Download the latest version of GIMP from www.gimp.org