First, Youtube and the screen use a lot of battery, so even though the screen is accountable for only 5% of the usage, that's 5% of a lot of usage (compared to, say, the alarm, which uses almost 0%).
Second, look at all the rest of the things using power. Since Youtube, at 6%, is the highest user, you probably have dozens of things running in the background - that you don't need. Install
SystemPanelLite to see what's running. Install
Greenify to keeps apps you don't need running from running.
Third, tap the graph to get to the next page, then post a screenshot. (If your Mobile network signal is all yellow or tan, you have a weak signal and that kills the battery.) So do so-called battery savers and system (or RAM) cleaners. If you're running anything by Cheetah Mobile, uninstall it.