You found a bike? Normally the process is to advise the local police station and hand it in. After 3-6 months you can legally claim ownership if the owner doesn't come forward, or the item goes to a periodic Police auction.
Cover yourself - don't risk get accused of stealing it.
The bike I can see in the pictures is missing some parts. At the bare minimum you will need to acquire
Front disk brake caliper, pads, and cable. And mounting bolts
EITHER Rear V brake arms, pads, cable and outer
OR Rear disk brake rotor, caliper, pads, cable, and bolts.
The rear brake depends on whether the hub has rotor mounts, and if the frame has caliper mounts for a disk brake, or if it has a rim brake track.
I also can't see a front derailleur, but the rear seems to be present.
Its certainly fixable, but you absolutely need two working brakes to ride it at all.
The brand does not matter in the slightest - it appears to be a 2005-2010 vintage, or perhaps a bit newer if its a BSO. The photos don't really show detail.