Simply copy all of your photos to your desktop/laptop computer. (If that's short of space too, plug a memory stick into a USB port and save them to that instead of to your computer's main drive). Then, irrespective of any cloud back-up you might have, you'll know that your images are safe.
If you want to be able to view your images on your phone, you'll either need to keep them on your phone or to use some form of cloud storage which lets you access them. If you've used Google Photos to back up your images, you'll be able to access them (from the cloud, rather than from your phone's storage) simply by opening the Google Photos app. (If you need further help, google for 'google photos tutorial').
You might also find it useful to create web albums on a site such as Flickr, which you can then access via your web browser.