Noisy brakes suck, esp on a new bike.
Looks like this has Magura MT5e hydraulic brakes? With this level of brake I wouldn't think it's heat or weight related, but JMO.
Since you've adjusted the brakes it sounds like sand or grit has gotten between the pads and the rotor. Can you get it up on a stand and spin the wheel? Same noise? If so, remove the wheel and blow out the caliper with compressed air. Remove and inspect the pads. Inspect the rotor. If there's no damage, clean the rotor and pad surfaces with alcohol. Install the cleaned pads and pry against them with plastic tire levers or a tool like this.;
https://www.parktool.com/product/hydraulic-brake-piston-press-pp-1-2. This will push the brake pistons back as far as they will go giving as much clearance for the pads as possible. This shouldn't be necessary for a new bike, but I edited this in so you can try everything in some logical order.
Install the wheel and test again for noise. If it persists it may be the rotor that's out of round and/or not centered correctly, i.e. more brake adjustment.
Does the noise get louder at the same angle of rotation? If so, the rotor needs to be trued. You can use an adjutable wrench but a tool like this:
https://www.parktool.com/product/rotor-truing-fork-dt-2 , is better. There are several good online videos on this technique.
If the noise is more or less continuous as the wheel rotates, the caliper is most likely not centered on the rotor. The basic technique is to loosen the caliper mounting screws, squeeze the brake and tighten the screws. Test for noise. If it still persists you need to fine adjust the caliper over the rotor and/or true the rotor as above. There are videos on this as well.
This can be an interative process so be patient.
In any event, I'd suggest a new LBS, or at least a new tech.
