Hello, I have the following question: What is the normal screen time of an iPhone 12 in normal use? In my case, the battery drops from 100 to 30 percent in 4 hours, is this normal? thanks in advance

Thank you for posting here in Apple Support Communities, radoslav146.

We understand that you have a few questions and concerns regarding your iPhone's battery usage, and we'd be happy to help. The normal screen time for an iPhone does vary from user to user. However, you can dive a bit further into this by tapping on "Show Activity" on that same screen and then checking the apps that have the most power consumption.

We'd also recommend that you use the battery maximizing tips found within the following resource: Batteries - Maximizing Performance - Apple

That resource addresses a few settings and features that can contribute to higher than normal power consumption. Once you've made the adjustments outlined in that article, we ask that you charge your iPhone to 100%, or overnight, and then continue to use it as you normally would for a full 24-hour period. 

During this period, please keep track of the battery drain. If there's no improvement after the 24-hour testing period, we'd recommend that you contact Apple Support for further assistance. Here's how: Get Support

Take care!