Free photo editing softwares with features as advanced as PhotoShop include:

GIMP: GIMP (GNU Image Manipulation Program) is a comprehensive image editing program developed by the free software community. It is designed to create creative outputs and can run on different operating systems. Download page of the program: GIMP download

Paint.NET: Paint.NET is a free image editing software designed for Microsoft Windows. It comes with a simple user interface and a variety of features. Download page of the program: Paint.NET download

Krita: Krita is an image editing program designed specifically for digital painting and drawing. This free and open source program works with different file formats. 

Pixlr: Pixlr is a web-based image editing program. Despite having many features, it is easy and intuitive to use.

Fotor: Fotor is an online image editing program. It comes with a simple user interface and fast processing features. Download page of the program: Fotor download

Inkscape: Inkscape is a vector graphics editor program that edits and creates drawings in SVG (Scalable Vector Graphics) format. It is free and open source. 

Canva: Canva is an online design platform that comes with a user-friendly interface and many features. It is designed especially for designs such as social media graphics, posters, logos, brochures. Download page of the program: Canva download

These programs allow you to edit your images for free and save them in different formats. Depending on your needs and preferences, you can edit your images using one of these programs. Especially with Gimp, you can perform image merging, photomontage, changing color tones, and applying filters professionally.