There are many apps which can be used to edit your smart phone photos. Also if you feel more comfortable, you can also edit any of your photos on your phone, or tablet.
A good starter app to use is #snapseed. This app applies an HDR filter that will enhance your photos. Beware not to over edit your photos. The 'grunge' edit on snapseed can be useful in applying a vintage look to your photos.
An app I use from time to time is #decim8. This can be a strong editing tool once you feel comfortable in using it to edit photos. Most times I will use it to get a version of a photo which I can then overlay onto the original photo. Interesting edits can be achieved using this technique.
A second app will be required for overlays. At first I was using the #blender app, but lately I have started back using the #laminar app. Laminar is close to #photoshop, and still easy to use. Good luck and happy editing.