This issue is easier to prevent than fixing in post.
Here the camera is pointed towards the sun. So the camera has to reduce how much light is taken in. As a consequence, the houses in the foreground appear as black silhouettes. This is exactly why backlight is a problem.
This is an overcast day with no direct sunlight. But the contrast between the bright white clouds and the dark horse is another illustration of the backlight problem. You can not see the details in the dark statue from Sofia.
This photo of a Swedish convenience store also has a problem with backlight. The front is too dark because the sunlight is coming from behind the storefront. Come back later or another day to get a much better shot where the storefront is nicely lit.
the backlight makes this church look way too dark.
This shot of the same church has other problems, but the backlight is not one of them.
Avoid contrasts so strong that your camera can not deal with them. Try to keep the sun and other strong light sources behind you. Come early or later for softer light or shoot on cloudy days.
Unfortunately, it is not possible to fix this issue in Google Photos. Snapseed and more advanced apps can brighten select areas. But the results will not be as good as selecting a better day or time of day to shoot.
You can try using HDR-mode if your camera has this option. See Use HDR when contrasts are huge (Tip # 13 at the bottom of the page).
The next issue is about contrast. You know the drill: Just hit "Suggested next page" below.