SRAM hydraulic brake weak - new bike I bought a new gravel bike (Serious Grafix Pro) with SRAM hydraulic disc brakes.
The rear one has very weak stopping power.

I can pull the right/rear brake lever completely to the handlebar and the pads just softly touch the rotor. So I'm wondering if I can just e.g. tighten a screw to make it more sensitive.

How can I adjust it? I found many Youtube videos, but none I needed.

Sorry for my lame question, not particularly strong for (not only) bike mechanics.

Thanks
Sounds like you need a brake bleed, as mentioned in the comments.  If there is air in a hydraulic system, the brake levers feel "spongy", or may not actuate the brake enough at all, which is what this sounds like.  Any time you can squeeze a brake lever all the way to the grip, that's a dangerously underpowered brake.  Brake bleeding is a process, and while you can do it yourself, it's usually recommended to take it to a shop, as it is easy to mess up, and messing up on a brake bleed can mean you ruin pads/hoses/calipers/levers, and can get costly.