Please update my iOS 12.5.7

If you can't upgrade beyond iOS 12, that is an indication that your iPhone is an older model. Many older models cannot be updated beyond a certain point because they lack the components to run newer software. Check the update eligibility for your phone to see if it is eligible for the update you are trying to get.

sorome wrote:

i can’t download apps fo iOS above 12.5.7.how I can upgrade my iOS or downloading all iOS software apps?

The only way is to replace your phone with a 6S or later.